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PIArg from Helianthus argophyllus is unlinked to other known downy mildew resistance genes in sunflower
Abstract
The PlArg locus in the sunflower (Helianthus annuus L.) inbred line Arg1575-2 conferring resistance to at least four tested races (300, 700, 730, 770) of downy mildew (Plasmopara halstedii) was localized by the use of simple sequence repeat (SSR) markers. Bulked segregant analysis (BSA) was conducted on 126 individuals of an F2 progeny from a cross between a downy mildew susceptible line, CmsHA342, and Arg1575-2. Twelve SSR markers linked to the PlArg locus were identified. All markers were located proximal to PlArg on linkage group LG1 based on the map of Yu et al. (2003) in a window of 9.3 cM. Since PlArg was mapped to a linkage group different from all other Pl genes previously mapped with SSRs, it can be concluded that PlArg provides a new source of resistance against P. halstedii in sunflower.
... Several molecular markers linked to the Plarg locus have been published in the literature [13,14,15]. The closer the gene and the molecular marker are to each other in the genetic map, the higher the probability that, as a result of recombination in meiosis of an F1 hybrid, the gene and the marker fragment will fall into the same gamete and be simultaneously passed on to the progeny. ...
... We assume that there is a segregation distortion of the whole genomic region, which is often observed in crosses of cultivated forms with wild species. similar segregation distortion was observed by Dußle et al. [14] in crosses of the susceptible line with another donor of Plarg gene introgressed from H. argophyllus, line Arg1575-2. The line RHA419 was obtained from a cross of RHA373 x Arg1575-2. ...
... So, according to C.M. Dußle et. al [14] SSR locus ORS509 is located at a distance of 1.9 cM from the Plarg gene. And according to Wieckhorst et al, a genetic map of linkage group LG1 was made, based on the study of the F2 generation of hybrid combination HA342 × ARG1575-2. ...
... Pl (Pl1-Pl17, Pl21 and Plarg) downy mildew resistance genes discovered to date in sunflowers and for the source of the Pl genes, wild Helianthus annual species can be followed [2]. These Pl genes that are very effective against P. halstedii races have been mapped in different linkage groups of sunflower: The Pl1/Pl6 locus on linkage group LG8 [3,4]; the Pl5/Pl8 and Pl21 loci on LG13 [5,6,7]; the Plarg locus on LG1 [8]; the Pl13, Pl14 and Pl16 loci on LG1 [8][9][10][11][12]. ...
... Pl (Pl1-Pl17, Pl21 and Plarg) downy mildew resistance genes discovered to date in sunflowers and for the source of the Pl genes, wild Helianthus annual species can be followed [2]. These Pl genes that are very effective against P. halstedii races have been mapped in different linkage groups of sunflower: The Pl1/Pl6 locus on linkage group LG8 [3,4]; the Pl5/Pl8 and Pl21 loci on LG13 [5,6,7]; the Plarg locus on LG1 [8]; the Pl13, Pl14 and Pl16 loci on LG1 [8][9][10][11][12]. ...
... Classical genetic analysis by phenotyping segregating populations elucidated that Plarg is unlinked to the previous known major resistance loci Pl1, Pl2, Pl5, Pl6, Pl7 and Pl8 which are mainly used in breeding material [34,35]. There are markers for several Pl genes, including Pl8, Pl13 and Plarg, which are still effective against all strains of P. halstedii [5,6,[8][9][10][11]13]. ...
The effectiveness of Pl genes is known to be resistant to downy mildew (DM) disease affected by fungus Plasmopara halstedii in sunflower. In this study phenotypic analysis was performed using inoculation tests and genotypic analysis were carried out with three DM resistance genes Plarg, Pl13 and Pl8 . A total of 69 simple sequence repeat markers and 241 F 2 individuals derived from a cross of RHA-419 (R) x P6LC (S), RHA-419 (R) x CL (S), RHA-419 (R) x OL (S), RHA419 (R) x 9758R (S), HA-R5 (R) x P6LC (S) and HA89 (R) x P6LC (S) parental lines were used to identify resistant hybrids in sunflower. Results of SSR analysis using markers linked with downy mildew resistance genes ( Plarg , Pl8 and Pl13 ) and downy mildew inoculation tests were evaluated together and ORS716 (for Plarg and Pl13), HA4011 (for Pl8 ) markers showed positive correlation with their phenotypic results. These results suggest that these markers are associated with DM resistance and they can be used successfully in marker-assisted selection for sunflower breeding programs specific for downy mildew resistance.
... argophyllus Torrey and Gray), a weed plant that inhabits sandy soils in south and southeast Texas [18]. H. argophyllus has been extensively used as a source of advantageous alleles for disease resistance [19], as well as for salt and drought tolerance [20], and insect resistance [12,21]. Comparative analysis has shown that hybrids of cultivated sunflowers with wild cytoplasmic male sterility (CMS) sources (H. ...
... The genome assemblies were validated by remapping reads with Bowtie 2 v2.3.5.1 [38] and visual revision of coverage uniformity (especially in the junctions of contigs) using Tablet v1. 19.09.03 [39]. For VIR114A, there was no sufficient sequencing data for de novo assembly and only mapping of reads to the reference mitogenome (MG735191.1) ...
Interspecific hybridization is widespread for sunflowers, both in wild populations and commercial breeding. One of the most common species that can efficiently cross with Helianthus annuus is the Silverleaf sunflower—Helianthus argophyllus. The current study carried out structural and functional organization analyses of mitochondrial DNA in H. argophyllus and the interspecific hybrid, H. annuus (VIR114A line) × H. argophyllus. The complete mitogenome of H. argophyllus counts 300,843 bp, has a similar organization to the mitogenome of cultivated sunflower, and holds SNPs typical for wild sunflowers. RNA editing analysis predicted 484 sites in H. argophyllus mitochondrial CDS. The mitochondrial genome of the H. annuus × H. argophyllus hybrid is identical to the maternal line (VIR114A). We expected that significant rearrangements in the mitochondrial DNA of the hybrid would occur, due to the frequent recombination. However, the hybrid mitogenome lacks rearrangements, presumably due to the preservation of nuclear–cytoplasmic interaction paths.
... argophyllus),, a sister species of H. annuus, is one of the most important donors. For example, it has been used as a donor of alleles for disease resistance [10][11][12][13][14][15][16][17] and drought tolerance [18,19]. Overall, it is the largest donor of genes to the cultivated sun ower, with approximately 5% of the genes in the cultivated sun ower were introgressed from H. argophyllus. ...
... The results showed that 75.12% (154 of 205 genes) of the H. argophyllus-speci c genes are related to disease resistance (Supplementary Table 3). This explains the strong and wide disease resistance of H. argophyllus and the successful practice of using H. argophyllus to enhance the disease resistance of cultivated sun ower [10][11][12][13][14][15][16][17]. It surprised us that there are also many genes (10.25%, 12 of 117 genes) speci c to H. annuus involved into disease resistance (Supplementary Table 4). ...
Background Silverleaf sunflower, Helianthus argophyllus , is one of the most important wild species that have been usually used for the improvement of cultivated sunflower. Although a reference genome is now available for the cultivated species, H. annuus , its effect in helping understanding the mechanisms underlying the traits of H. argophyllus is limited by the substantial genomic variance between these two species.
Results In this study, we generated a high-quality reference transcriptome of H. argophyllus using Iso-seq strategy. This assembly contains 50,153 unique genes covering more than 91% of the whole genes. Among them, we find 205 genes that are absent in the cultivated species and 475 fusion genes containing components of coding or non-coding sequences from the genome of H. annuus . It is interesting that in line with the strong disease resistance observed for H. argophyllus , these H. argophyllus -specific genes are predominantly related to functions of resistance. We have also profiled the gene expressions in leaf and root under normal or salt stressed conditions and, as a result, find distinct transcriptomic responses to salt stress in leaf and root. Particularly, genes involved in several critical processes including the synthesis and metabolism of glutamate and carbohydrate transport are reversely regulated in leaf and root.
Conclusions Overall, this study provided insights into the genomic mechanisms underlying the disease resistance and salt tolerance of silverleaf sunflower and the transcriptome assembly and the genes identified in this study can serve as a complement data resources for future research and breeding programs of sunflowers.
... It has been known in cultivation as the 'silver leaf sunflower' since 1889 (Heiser Jr., 1951). Strong research interest in H. argophyllus has been developed because populations of this species contain dominant genes conferring resistance to all known races of downy mildew which have been incorporated into inbred lines of cultivated sunflower (Miller and Gulya, 1988;Seiler, 1991;Miller et al., 2002;Dussle et al., 2004;Jan and Gulya, 2006). Silver leaf sunflower is the closest relative of common sunflower (Schilling and Heiser, 1981), widely used in sunflower breeding as donor of disease resistance alleles (Heiser Jr, 1951;Miller and Gulya, 1991;Slabaugh et al., 2003;Dussle et al., 2004;Radwan et al., 2004;Seiler et al., 2007), fertility restoration to PET1 cytoplasm (Chepurnaya et al., 2003) (Horn et al., 2002). ...
... Strong research interest in H. argophyllus has been developed because populations of this species contain dominant genes conferring resistance to all known races of downy mildew which have been incorporated into inbred lines of cultivated sunflower (Miller and Gulya, 1988;Seiler, 1991;Miller et al., 2002;Dussle et al., 2004;Jan and Gulya, 2006). Silver leaf sunflower is the closest relative of common sunflower (Schilling and Heiser, 1981), widely used in sunflower breeding as donor of disease resistance alleles (Heiser Jr, 1951;Miller and Gulya, 1991;Slabaugh et al., 2003;Dussle et al., 2004;Radwan et al., 2004;Seiler et al., 2007), fertility restoration to PET1 cytoplasm (Chepurnaya et al., 2003) (Horn et al., 2002). It was also reported as a source of favourable alleles for salt and drought tolerance (Rauf, 2008) and insect resistance (Rogers and Thompson, 1980;Rogers et al., 1987;Sujatha and Lakshminarayana, 2007). ...
Native Bacillus species screened from rhizosphere of Sesame (Sesamum indicum L.) were tested for their growth promoting and antagonistic effects. Based on 16S rRNA gene sequence based homology, the bacterial isolates were identified as B. amyloliquefaciens, B. aryabhattai, B. cereus, B. flexus, B. megaterium, B. methylotrophicus, B. pumilus and B. subtilis. Results on biochemical characterization of Bacillus species indicated that majority of the isolates were producing catalsae and were found to be diazotrophs. Only few isolates were found to produce protease, cellulase and HCN. Only one isolate (B. amyloliquefaciens) was found to be phosphate solubilizer. Further, in vitro antagonistic assay revealed that Bacillus subtilis and B. methylotrophicus could inhibit the mycelial growth of M. phaseolina by 30.9 and 29.0 per cent, respectively. Majority of the Bacillus species tested have increased sesame seed germination, radicle and plumule length compared to control. Overall, our results suggested the scope and potentiality of Bacillus species in promoting sesame seed germination and growth besides pathogen suppression.
... There is no rescue treatment once the disease manifests. The inbred line RHA 464 carries a rust R gene, R12, as well as a broad-spectrum DM R gene, PlArg, which is resistant to all P. halstedii races [29][30][31][32][33]. PlArg has recently been genetically and physically mapped using high-density single nucleotide polymorphism (SNP) markers on chromosome 1, and the 12 diagnostic SNP markers co-segregating with PlArg span a physical distance of 34.5 Mb, due to suppressed recombination [25]. ...
... PlArg was originally transferred from a wild H. argophyllus into cultivated sunflower in 1989 with no reports of resistance breakdown for more than 25 years [31,33,46]. Molecular mapping placed PlArg in a region with highly suppressed recombination on sunflower chromosome 1 [30,47]. Qi et al. [25] reported that 78 SNP markers co-segregated with PlArg in an F2 population derived from the cross of HA 89/RHA 464, and 12 of them were diagnostic for PlArg, which spanned a physical distance of 34.5 Mb (between 106.0 Mb and 140.5 Mb) in the HA412-HO genome assembly (Table 2). ...
Rust caused by the fungus Puccinia helianthi and downy mildew (DM) caused by the obligate pathogen Plasmopara halstedii are two of the most globally important sunflower diseases. Resistance to rust and DM is controlled by race-specific single dominant genes. The present study aimed at pyramiding rust resistance genes combined with a DM resistance gene, using molecular markers. Four rust resistant lines, HA-R3 (carrying the R4 gene), HA-R2 (R5), HA-R8 (R15), and RHA 397 (R13b), were each crossed with a common line, RHA 464, carrying a rust gene R12 and a DM gene PlArg. An additional cross was made between HA-R8 and RHA 397. Co-dominant simple sequence repeat (SSR) and single nucleotide polymorphism (SNP) markers linked to the target genes were used to discriminate between homozygotes and heterozygotes in F2 populations. Five pyramids with different combinations of rust resistance genes were selected in the homozygous condition through marker-assisted selection, and three of them were combined with a DM resistance gene PlArg: R4/R12/PlArg, R5/R12/PlArg, R13b/R12/PlArg, R15/R12, and R13b/R15. The pyramiding lines with the stacking of two rust and one DM genes were resistant to all known races of North American sunflower rust and all known races of the pathogen causing DM, potentially providing multiple and durable resistance to both rust and DM. A cluster of 12 SNP markers spanning a region of 34.5 Mb on chromosome 1, which co-segregate with PlArg, were tested in four populations. Use of those markers, located in a recombination suppressed region in marker selection, is discussed.
... The seven DM R genes, Pl Arg , Pl 13 , Pl 14 , Pl 16 , and Pl 23 -Pl 25 have been previously mapped to LG1 of the sunflower genome (Dußle et al. 2004;Mulpuri et al. 2009;Bachlava et al. 2011;Liu et al. 2012;Pecrix et al. 2018b). Pl 13 , Pl 14 , Pl 16 , and Pl 25 are located on the lower end of LG1 and cluster together, while the cluster of Pl Arg , Pl 23 , and Pl 24 is far from this gene cluster in LG1 Pecrix et al. 2018b). ...
... Sunflower crop wild relatives, especially wild H. annuus and H. argophyllus, have contributed most of the DM R genes for cultivated sunflower and play an important role in the control of DM in sunflower production (Table S1, Vear et al. 2008b;Qi et al. 2015Qi et al. , 2016Ma et al. 2017;Zhang et al. 2017;Pecrix et al. 2018a, b). Among the 29 mapped DM R genes (Pl 1 , Pl 2 , Pl 5 -Pl 8 , Pl 13 -Pl 35 , Pl Arg ), five, Pl Arg , Pl 8 , Pl 18 , Pl 20 , and Pl 35 , were introgressed from H. argophyllus, and four (Pl Arg , Pl 8 , Pl 18 , and Pl 20 ) were previously mapped to four LGs, 1, 13, 2, and 8, of the sunflower genome (Dußle et al. 2004;Bachlava et al. 2011;Qi et al. 2016;Ma et al. 2017). In the present study, we mapped Pl 35 derived from wild H. argophyllus to LG1, which is the first Pl gene from H. argophyllus mapped to the same chromosome as Pl Arg . ...
Key message
We have mapped a new downy mildew resistance gene, Pl35, derived from wild Helianthus argophyllus to sunflower linkage group 1. New germplasms incorporating the Pl35 gene were developed for both oilseed and confection sunflower
Abstract
Sunflower downy mildew (DM), caused by the oomycete pathogen Plasmopara halstedii, is an economically important and widespread sunflower disease worldwide. Non-race-specific resistance is not available in sunflower, and breeding for DM resistance relies on race-specific resistance to control this disease. The discovery of the novel DM resistance genes is a long-term task due to the highly virulent and aggressive nature of the P. halstedii pathogen, which reduces the effectiveness of resistance genes. The objectives of this study were to: (1) transfer DM resistance from a wild sunflower species Helianthus argophyllus (PI 494576) into cultivated sunflowers; (2) map the resistance gene; and (3) develop diagnostic single-nucleotide polymorphism (SNP) markers for efficient targeting of the gene in breeding programs. The H. argophyllus accession PI 494576 previously identified with resistance to the most virulent P. halstedii race 777 was crossed with oilseed and confection sunflower in 2012. Molecular mapping using the BC2F2 and BC2F3 populations derived from the cross CONFSCLB1/PI 494576 located a new resistance gene Pl35 on linkage group 1 of the sunflower genome. The new gene Pl35 was successfully transferred from PI 494576 into cultivated sunflowers. SNP markers flanking Pl35 were surveyed in a validation panel of 548 diversified sunflower lines collected globally. Eleven SNP markers were found to be diagnostic for Pl35 SNP alleles, with four co-segregating with Pl35. The developed oilseed and confection germplasms with diagnostic SNP markers for Pl35 will be very useful resources for breeding of DM resistance in sunflower.
... Spores move towards the roots and penetrate into the tissue, thereby initiating primary infection (Virányi and Spring 2011). Infected plants tend to be insufficiently developed, dwarfed, with chlorotic leaves covered with white mycelium (Dussle et al. 2004). The extent of the damage that the pathogen causes is influenced by several factors: ...
... Concerning Plarg gene, the majority of identified and developed markers belong to SSR, SNP and NBS-LRR (nucleotide-binding site-leucine-rich repeat) RGCs type. Dussle et al. (2004) and Wieckhorst et al. (2010) identified flanking and cosegregating markers to the gene, respectively. Cosegregating markers ORS 716, HT722 and HT211 in addition to NBS-LRR RGCs (RGC151, RGC52a and RGC52b) markers were identified by Wieckhorst et al. (2010), while Imerovski et al. (2014) confirmed cosegregation of previously reported SSR markers and reported another cosegregating SSR ORS 675 and validated the markers across different sunflower genetic backgrounds. ...
Due to its ability to grow in different agroecological conditions and its moderate drought tolerance, sunflower may become the oil crop of preference in the future, especially in the light of global environmental changes. In the field conditions, sunflower crop is often simultaneously challenged by different biotic and abiotic stresses, and understanding the shared mechanisms contributing to two or more stresses occurring individually or simultaneously is important to improve crop productivity under foreseeable complex stress situations. Exploitation of the available plant genetic resources in combination with the use of modern molecular tools for genome-wide association studies (GWAS) and application of genomic selection (GS) could lead to considerable improvements in sunflower, especially with regard to different stresses and better adaptation to the climate change. In this chapter we present a review of climate-smart (CS) traits and respective genetic resources and tools for their introduction into the cultivated sunflower, thus making it the oil crop resilient to the extreme climatic conditions and well-known and emerging pests and diseases.
... CONFSCLR5 is susceptible to DM and rust. RHA 464 (PI 665015) is an oilseed restorer line released by the USDA-ARS and the North Dakota Agricultural Experiment Station in 2010 resistant to all North American DM and rust races identiied to date (Hulke et al., 2010a;Gong et al., 2013a;Gilley et al., 2015). he DM and rust R genes in RHA 464 were named Pl Arg and R 12 and mapped to linkage groups (LGs) 1 and 11 of the sunlower genome, respectively (Dußle et al., 2004;Gong et al., 2013b;Talukder et al., 2014;Qi et al., 2017). HA-DM2 was developed by the backcross breeding method, with selection in each generation for DM and rust resistance. he initial cross was made between CONFSCLR5 and RHA 464 in 2014, and the F 1 hybrids were sequentially tested with P. halstedii race 734 and P. helianthi race 336. he selected plants were backcrossed four times to the recurrent parent CONFSCLR5. ...
... he DM and rust resistance in HA-DM2 is conditioned separately by two single dominant genes, Pl Arg and R 12 , located on LG1 and LG11 of sunlower genome (Dußle et al., 2004;Gong et al., 2013b;Talukder et al., 2014;Qi et al., 2017). Two lanking SNP markers for each gene, NSA_002798 and NSA_001835 for Pl Arg , and NSA_003320 and NSA_001570 for R 12 were used to test 184 HA-DM2 plants. ...
Downy mildew (DM) and rust are two destructive diseases in sunflower (Helianthus annuus L.) production worldwide that limit yield and reduce seed quality. Combining different disease resistance (R) genes in a single genotype of sunflower can increase the field performance due to host resistance. The confection sunflower germplasm lines HA‐DM2 (Reg. No. GP‐350, PI 687022), HA‐DM3 (Reg. No. GP‐351, PI 687023), and HA‐DM4 (Reg. No. GP‐352, PI 687024), developed using backcrossing, pedigree breeding, and DNA marker‐assisted selection, were released by the USDA‐ARS Sunflower and Plant Biology Research Unit in collaboration with the North Dakota Agricultural Experiment Station in June 2017. HA‐DM2 harbors the DM R gene, PlArg, and rust R gene, R12, both transferred from an oilseed sunflower line RHA 464. HA‐DM3 harbors the DM R gene, Pl17, and rust R gene, R13a, transferred from an oilseed line HA 458 and confection line HA‐R6, respectively. HA‐DM4 harbors the DM R gene, Pl18, and rust R gene, R13a, transferred from an oilseed line HA‐DM1 and confection line HA‐R6, respectively. Phenotypic and marker testing for DM and rust confirmed that the BC4F4–derived HA‐DM2, HA‐DM3, and HA‐DM4 germplasm each harbors DM and rust R genes in the homozygous condition and are resistant to all DM and rust races identified in North America to date. These disease‐resistant lines are a valuable contribution for breeding‐enhanced DM and rust resistance in confection sunflower in North America and globally.
... (H. praecox, H. argophyllus) [13][14][15][16][17], but Pl5, in Progress and Novinka was reported to have come from H. tuberosus [18], and perennial Helianthus species are certainly resistant. It may be noted that some genes give resistance to a large number of races and some races are controlled by several different genes. ...
... This cluster appeared to group Pl genes from many different sources, H. annuus, H. argophyllus and H. tuberosus, but, since the genome of a sunflower line, XRQ, carrying Pl5, has been sequenced [28] and it has been shown that the lower part of LG13 carries many sequences from H. argophyllus, it may be questioned whether the materiel bred by G. pustovoit really came from a cross with H. tuberosus. Plarg, together with Pl13, Pl14 and Pl16, are localized on LG1, although quite widely spaced [14,29,30]. More recently, Pl genes giving resistance to all known races have also been mapped to LG2 (Pl18) and LG4 (Pl17, Pl19) [16,17,31]. ...
The main diseases of sunflower which can be controlled by major genes are downy mildew, broomrape, rust and Verticillium wilt, whereas the crop shows quantitative resistance to Sclerotinia rots and wilt, phomopsis stem canker, Phoma premature ripening and black stem and Alternaria. Over the past 40 years, knowledge of the genetics of resistance to all these diseases has increased, but it is only for major gene resistance that marker-assisted selection is used routinely in breeding. Improvement of quantitative resistances still depends largely on field observations, markers are not yet used to select favourable alleles at quantitative trait loci. Genomic selection could be a means to improve quantitative resistances at a low cost, if RIL populations or core collections phenotyped in the past have been maintained.
... As a broad-spectrum Pl gene that has been used in breeding programs for more than two decades, Pl Arg is still effective against all known races of P. halstedii and is able to control downy mildew for an extended period of time (Gascuel et al. 2015;Gilley et al. 2016). Dußle et al. (2004) first reported the mapping of Pl Arg on LG1 of the sunflower genome using SSR markers. Wieckhorst et al. (2010) identified two RGC markers that co-segregated with Pl Arg . ...
... The downy mildew resistance gene Pl Arg in ARG-1575 was previously mapped to LG1 of the sunflower genome (Dußle et al. 2004). In the present study, the genetic map of LG1 was constructed by integrating SNP genotypic data and DM phenotypic data using an F 2 population derived from a cross of HA 89/RHA 464, which was previously used in a SNP mapping project (Talukder et al. 2014). ...
Diagnostic DNA markers are an invaluable resource in breeding programs for successful introgression and pyramiding of disease resistance genes. Resistance to downy mildew (DM) disease in sunflower is mediated by Pl genes which are known to be effective against the causal fungus, Plasmopara halstedii. Two DM resistance genes, PlArg and Pl8, are highly effective against P. halstedii races in the USA, and have been previously mapped to the sunflower linkage groups (LGs) 1 and 13, respectively, using simple sequence repeat (SSR) markers. In this study, we developed high-density single nucleotide polymorphism (SNP) maps encompassing the Plarg and Pl8 genes and identified diagnostic SNP markers closely linked to these genes. The specificity of the diagnostic markers was validated in a highly diverse panel of 548 sunflower lines. Dissection of a large marker cluster co-segregated with PlArg revealed that the closest SNP markers NSA_007595 and NSA_001835 delimited PlArg to an interval of 2.83 Mb on the LG1 physical map. The SNP markers SFW01497 and SFW06597 delimited Pl8 to an interval of 2.85 Mb on the LG13 physical map. We also developed sunflower lines with homozygous, three gene pyramids carrying PlArg, Pl8, and the sunflower rust resistance gene R12 using the linked SNP markers from a segregating F2 population of RHA 340 (carrying Pl8)/RHA 464 (carrying PlArg and R12). The high-throughput diagnostic SNP markers developed in this study will facilitate marker-assisted selection breeding, and the pyramided sunflower lines will provide durable resistance to downy mildew and rust diseases.
... • All germplasms confer comprehensive resistance to all races of downy mildew and rust identified so far. in 1988in and 2010in , respectively (Abritti et al., 2008Hulke et al., 2010b;Miller & Gulya, 1988). RHA 340 possesses a DM resistance (R) gene (Pl 8 ) mapped to linkage group (LG) 13 of the sunflower genome, and RHA 464 carries a DM R gene (Pl Arg ) mapped to LG1 and a rust R gene (R 12 ) mapped to LG11 (Bachlava et al., 2011;Dußle et al., 2004;Gong et al., 2013). HA 458 (PI 655009) and HA-DM1 (PI 674793) are oilseed maintainer lines released in 2010 and 2016, respectively (Hulke et al., 2010a;Qi & Seiler, 2016b). ...
Downy mildew (DM) and rust are two major global sunflower (Helianthin annuus L.) diseases causing significant yield losses and reducing seed quality. Host plant resistance mediated by dominant race‐specific genes has been extensively used in sunflower production to control these diseases. However, the considerable variability of the DM and rust pathogens caused by mutation or recombination has changed the dynamics of the diseases, significantly increasing their incidence in recent years. This necessitates the development and release of sunflower germplasm with enhanced levels of disease resistance. Germplasm lines HA‐DM12 (Reg. no. GP‐382, PI 700006), HA‐DM13 (Reg. no. GP‐383, PI 700007), and HA‐DM14 (Reg. no. GP‐384, PI 700008), all with multiple DM and rust resistance, were developed using phenotypic evaluation and marker‐assisted selection. The three lines share a common DM gene (PlArg) and a rust gene (R12) and a combination of different DM genes (Pl8, Pl17, and Pl18, respectively). The triple‐gene pyramids—HA‐DM12 (Pl8Pl8/PlArgPlArg/R12R12), HA‐DM13 (Pl17Pl17/PlArgPlArg/R12R12), and HA‐DM14 (Pl18Pl18/PlArgPlArg/R12R12)—confer comprehensive resistance to all races of DM and rust identified so far and can be used in sunflower breeding programs to develop hybrids with durable resistance to DM and rust.
... Carriers of the PlARG gene, which determines the universal resistance against all known races of Plasmopara helianthi, are the most valuable sources of resistance in further sunflower breeding for resistance to downy mildew (Jocić et al., 2010). The PlARG gene was mapped with SSR markers in linkage group (LG) 1 of the sunflower genetic map (Duble et al., 2004), and it was shown to be closely linked with microsatellites ORS716, ORS509, ORS1128, and ORS543 (Wieckhorst et al., 2010). ...
Recently, the problem of phytosanitary condition of sunflower crops has been exacerbated, which is associated with violation of crop rotations and, as a consequence, spread of common diseases. Selection for resistance to biotic factors requires comprehensive research into the crop biology and pathogens. The use of starting material, which is resistant to major pathogens and environmental stressors, in selection is a prerequisite for the breeding of highly productive hybrids. Significant progress in the breeding of heterosis sunflower hybrids has been achieved primarily due to stable inbred lines. However, their creation is time-consuming, taking 8-12 years. Selection of desirable genotypes and initial forms for crossing is complicated by the fact that it is driven by a set of polygenic traits that are prone to significant modification variability. The use of molecular genetic markers is a way to accelerate breeding. Marker-assisted selection breeding (MAS) has been theoretically justified in numerous publications and implemented in most breeding institutions around the world. However, in domestic breeding programs, MAS has not become widespread compared to traditional methods. Nevertheless, this breeding trend opens new opportunities for studying genetic diversity and determining kinship at the intraspecies and genus levels. The review provides information on the status and prospects of implementation of MAS in traditional plant breeding and highlights the achievements of modern biotechnology in sunflower breeding for resistance to biotic factors owing to molecular genetic markers. The MAS principles are outlined and the advantages of this method are described. Specific examples of application of the molecular approach during the development of starting material of sunflower for breeding for resistance to common diseases and parasites are given. The main stages and components of PCR analysis are also described. Inbred sunflower lines – carriers of the gene for resistance to the downy mildew pathogen are characterized and genetic passports using STS markers to the Pl6 locus have been formalized for 13 sunflower lines.
... Lastly, Pl 30 was the first downy mildew resistance to be located on LG11 (Pecrix et al. 2018). In summary, at least 20 major genes of resistance to downy mildew (Pl 1 , Pl 2 , Pl 5 -Pl 8 , Pl 13 -Pl 19 , Pl 21 , Pl 22 , Pl 30 , Pl 33 , Pl 34 , Pl 35 , and Pl Arg ) have been assigned to specific LGs 1, 2, 4, 8, 11 and 13 of the sunflower genome (Mouzeyar et al. 1995;Roeckel-Drevet et al. 1996;Vear et al. 1997;Bert et al. 2001;Yu et al. 2003;Dußle et al. 2004;Mulpuri et al. 2009;Bertero de Romano et al. 2010;Bachlava et al. 2011;Liu et al. 2012Liu et al. , 2019Qi et al. 2015Qi et al. , 2016Qi et al. , 2019Zhang et al. 2016;Pecrix et al. 2018Pecrix et al. , 2019Talukder et al. 2019). ...
The breeding of sunflower (Helianthus annuus L.) for resistance to downy mildew (caused by the oomycete Plasmopara halstedii Farl. Berl. & de Toni) is reviewed in this work under the scope of its sustainability and efficiency. When sunflower turned into an oilseed crop, resistance to the disease was included in its initial breeding strategies. Subsequent development of genomic tools allowed a significant expansion of the knowledge on the diversity of its genetic resistance and its application to the genetic control of the disease. Simultaneously to genetic improvements, and as a consequence of the close interaction between the pathogen and its host plant, an enormous variety of pathotypes has been described in all the sunflower-growing areas worldwide. Thus, the genetic control of sunflower downy mildew is an active research field subjected to continuous evolution and challenge. In practice, genetic resistance constitutes the base tier of Integrated Pest Management against sunflower downy mildew. The second tier is composed of elements related to crop management: rotation, removal of volunteer plants, sowing date, tillage. Biological control alternatives and resistance inducers could also provide additional restraint. Finally, the top tier includes chemical treatments that should only be used when necessary and if the more basal Integrated Pest Management elements fail to keep pathogen populations under the economic threshold.
... Resistance against DM in sunflower is governed by single dominant genes, designated as Pl. Sunflower inbred line RHA 464 carries a rust R gene, R 12 , as well as a broad-spectrum DM R gene, Pl Arg , which is resistant to all P. halstedii races (Dußle et al., 2004;Gong et al., 2013b;Gilley et al., 2020). RHA 464 was used as a common parent in this study. ...
Rust and downy mildew (DM) are two of the most important sunflower diseases in the world. The development of sunflower hybrids with enhanced levels of genetic resistance to both diseases is a goal for sunflower breeding. Four oilseed sunflower (Helianthus annuus L.) germplasm lines, HA‐R14 (Reg. no. GP‐371, PI 698193), HA‐R15 (Reg. no. GP‐372, PI 698194), HA‐R16 (Reg. no. GP‐373, PI 698195), and HA‐R17 (Reg. no. GP‐374, PI 698196) are multiple rust‐ and DM‐resistant lines that were developed and released by the USDA‐ARS Sunflower and Plant Biology Research Unit in collaboration with the North Dakota Agricultural Experiment Station in January 2020. Three lines, HA‐R14 (R4R4/R12R12/PlArgPlArg), HA‐R15 (R5R5/R12R12/PlArgPlArg), and HA‐R16 (R13bR13b/R12R12/PlArgPlArg), stack two different rust genes with a common DM gene PlArg, and HA‐R17 (R13bR13b/R15R15) possesses two rust genes, R13b and R15. These germplasm lines will provide a broad spectrum of useful sources of resistance to all known races of rust and DM.
... Gènes Pl : (Rahim et al. 2002;Dussle et al. 2004;Mulpuri et al. 2009 ...
Les variétés traditionnelles de vigne nécessitent de très nombreux traitements phytosanitaires pour lutter contre les maladies cryptogamiques qui touchent leurs parties herbacées, comme le mildiou et l’oïdium, causés par Plasmopara viticola et Erysiphe necator respectivement. Ces traitements, coûteux et préjudiciables pour l'environnement, pourraient être réduits par l’emploi de variétés résistantes. La vigne cultivée européenne (Vitis vinifera, 2n=38) est très sensible au mildiou et à l'oïdium. En conséquence, la résistance doit être introduite à partir d’autres Vitaceae ayant un niveau de résistance plus élevé à ces maladies. Plusieurs origines de résistance ont déjà été observées et inventoriées, en particulier chez l’espèce d’origine américaine Muscadinia rotundifolia (2n=40). Ces facteurs sont d'un intérêt majeur pour la sélection de variétés résistantes. Cependant, lors du processus d'introgression, des difficultés à obtenir des pépins viables en F1 ainsi que des anomalies phénotypiques dans les descendances en rétrocroisement ont été constatées. Afin d’optimiser la gestion des résistances provenant de cette espèce dans les programmes d’amélioration variétale, il est nécessaire de comprendre l’organisation génétique et génomique de M. rotundifolia, et de compléter la connaissance des facteurs de résistance issus de cette espèce. Dans ce contexte, les objectifs de la thèse sont : (i) de réaliser une analyse comparative des génomes de V. vinifera et M. rotundifolia et (ii) d’identifier de nouveaux facteurs de résistance chez M. rotundifolia utilisables à terme en sélection. Pour cela, une carte génétique de M. rotundifolia a été développée à partir d’une population de 200 individus issue de l’autofécondation de M. rotundifolia cv. Regale. Parallèlement, la même population a été testée pour son niveau de résistance au mildiou et à l’oïdium. Une carte génétique couvrant 950 cM a été réalisée. Elle comprend 191 marqueurs microsatellites répartis sur les 20 chromosomes de M. rotundifolia, et permet de conclure à un niveau de macrosynténie très élevé avec V. vinifera. Le groupe de liaison 20 de M. rotundifolia correspondrait à la partie inférieure du groupe de liaison 7 de V. vinifera. Par ailleurs, un QTL de résistance au mildiou a été détecté sur le groupe de liaison 18 de M. rotundifolia, au niveau d’une région riche en gènes de type NBS-LRR, et un nouveau QTL de résistance majeur à la l’oïdium a été mis en évidence sur le groupe de liaison 14 de M. rotundifolia. Ce QTL, nommé Ren5 pour ‘Resistance to Erysiphe necator 5’, montre une action précoce dans l’arrêt de la croissance du mycélium du pathogène, dès l’établissement des premiers stades de biotrophie du champignon. De plus, le QTL Ren5 a été confronté à deux souches supplémentaires d’E. necator, appartenant aux deux groupes d’oïdium retrouvés dans vignobles européens, contre lesquelles il reste efficace. Les données de cartographie génétique générées pour M. rotundifolia dans ce travail, ainsi que la mise en évidence de Ren5 et de son mode d’action, permettront d’améliorer la gestion des facteurs de résistance issus de cette espèce pour la sélection de variétés résistantes au mildiou et à l’oïdium.
... This new line is highly resistant to all P. halstedii races identified in the US providing breeders with an effective new source of resistance against downy mildew in sunflower. Pl Arg and Pl 8 both originating from the wild H. argophyllus were previously mapped to LGs1 and 13, respectively (Dußle et al. 2004;Bachlava et al. 2011). An F 2 population of 140 individuals from the cross of HA 89 and RHA 464 harboring Pl Arg and R 12 was previously used as a mapping population to map SNP markers in the sunflower genome of the National Sunflower Association (NSA) SNP Consortium project (Talukder et al. 2014c). ...
Rust, downy mildew (DM), and Sclerotinia diseases are the major yield limiting factors in global sunflower production. The use of resistant hybrids, where available, is the most efficient measure of controlling these diseases. Development of DNA markers linked to the resistance genes will facilitate molecular breeding of disease-resistant hybrids in sunflower. We have molecularly mapped seven rust R-gene loci, R 2 , R 4 , R 5 , R 11 , R 12 , R 13a, and R 13b to linkage groups (LG) of the sunflower genome, developed both simple sequence repeat (SSR) and single nucleotide polymorphism (SNP) markers linked to these R-genes, and used them in marker-assisted gene pyramiding in sunflower. Two new DM R-genes, Pl 17 and Pl 18 , were mapped to LGs 4 and 2 of the sunflower genome, respectively, different from all known DM R-genes previously mapped to LGs 1, 8, and 13. Pl 18 was recently transferred from H. argophyllus into cultivated sunflower. We also identified diagnostic SNP markers linked to the DM R-genes, Pl Arg and Pl 8. Quantitative trait loci (QTL) for Sclerotinia basal stalk rot resistance were identified in a sunflower recombinant inbred line population derived from the cross HA 441/RHA 439 using genotyping-by-sequencing approach. A total of six QTL were identified, one each on linkage groups (LGs) 4, 9, 10, 11, 16 and 17, each explaining between 6 and 29% of the observed phenotypic variance in the RIL population. The QTL on LGs 10 and 17 were detected in multiple environments with very high LOD values (5.49-12.01), while the remaining QTL were detected in single environment. A combined analysis with integrated phenotypic data across environments also detected the QTL on LGs 10 and 17, each explaining 32 and 20%, respectively of the phenotypic variation for the trait.
... Unlike BSR, DM resistance is largely governed by pathotype-specific major genes with complete resistance. More than 20 DM resistance (R) genes, denoted by Pl, have been identified in sunflower conferring resistance to one or more pathotypes of P. halstedii, (Mouzeyar et al., 1995;Dußle et al., 2004;Mulpuri et al., 2009;Bachlava et al., 2011;Liu et al., 2012;Vincourt et al., 2012;Qi et al., 2015Qi et al., , 2016Zhang et al., 2017;Ma et al., 2017). These R genes have been used routinely in commercial sunflower breeding programs for developing DMresistant hybrids. ...
Sclerotinia basal stalk rot (BSR) and downy mildew (DM) are agronomically important diseases of sunflower (Helianthus annuus L.) worldwide. Three sunflower germplasm lines, HA‐BSR6 (Reg. no. GP‐353, PI 685019), HA‐BSR7 (Reg. no. GP‐354, PI 685020), and HA‐BSR8 (Reg. no. GP‐355, PI 685021), were developed with dual resistance to both BSR and DM. Their resistance to BSR was transferred from the wild annual sunflower H. praecox subsp. runyonii Engelmann & A. Gray (Heiser) (PI 468853), and DM resistance was introgressed from inbred line HA 458 possessing the Pl17 gene. The germplasms were tested for BSR resistance in inoculated field trials in multiple locations over 4 yr. All three germplasm lines showed significantly higher BSR resistance (p < 0.05) than the recurrent parent and the checks across environments, with a 4‐yr mean disease incidence (DI) ranging from 1.2 to 4.8%, while ‘Cargill 270’ (susceptible hybrid check) and HA 89 (recurrent parent) had DI of 36.1 and 31.0%, respectively, and HA 441 (resistant inbred check) and ‘Croplan 305’ (resistant hybrid check) had DI of 19.5 and 11.6%, respectively. Whole genome scan using genotyping‐by‐sequencing revealed the presence of H. praecox subsp. runyonii chromosome segments in HA‐BSR6, HA‐BSR7, and HA‐BSR8, which are potentially associated with BSR resistance. Phenotypic evaluation identified DM resistance in all three germplasm lines, with flanking DNA markers confirming the presence of the Pl17 gene in the lines. These germplasm lines can be used in sunflower breeding programs for pyramiding both BSR and DM resistance genes.
... Berl. Et de Toni) and are routinely being deployed into cultivated sunflower as race-specific single dominant genes [15][16][17][18][19][20]. Earlier studies have repeatedly demonstrated high level of Sclerotinia resistance in the wild Helianthus gene-pool (reviewed by Seiler et al. [14]). ...
Sclerotinia basal stalk rot (BSR) and downy mildew are major diseases of sunflowers worldwide. Breeding for BSR resistance traditionally relies upon cultivated sunflower germplasm that has only partial resistance thus lacking an effective resistance against the pathogen. In this study, we report the transfer of BSR resistance from sunflower wild species, Helianthus praecox, into cultivated sunflower and molecular assessment of the introgressed segments potentially associated with BSR resistance using the genotyping-by-sequencing (GBS) approach. Eight highly BSR-resistant H. praecox introgression lines (ILs), H.pra 1 to H.pra 8, were developed. The mean BSR disease incidence (DI) for H.pra 1 to H.pra 8 across environments for four years ranged from 1.2 to 11.1%, while DI of Cargill 270 (susceptible check), HA 89 (recurrent parent), HA 441 and Croplan 305 (resistant checks) was 36.1, 31.0, 19.5, and 11.6%, respectively. Molecular assessment using GBS detected the presence of H. praecox chromosome segments in chromosomes 1, 8, 10, 11, and 14 of the ILs. Both shared and unique polymorphic SNP loci were detected throughout the entire genomes of the ILs, suggesting the successful transfer of common and novel introgression regions that are potentially associated with BSR resistance. Downy mildew (DM) disease screening and molecular tests revealed that a DM resistance gene, Pl17, derived from one of the inbred parent HA 458 was present in four ILs. Introgression germplasms possessing resistance to both Sclerotinia BSR and DM will extend the useful diversity of the primary gene pool in the fight against two destructive sunflower diseases.
... To combat this destructive disease, the major genes for host race-specific resistance, denoted as Pl, have been deployed on a large scale in sunflower production since the 1990s (Albourie et al. 1998;Gulya et al. 1999Gulya et al. , 2011. At least 16 Pl resistance (R) genes have been mapped on linkage groups (LGs) 1 (Pl Arg , Pl 13 , Pl 14 , and Pl 16 ), 2 (Pl 18 ), 4 (Pl 17 and Pl 19 ), 8 (Pl 1 , Pl 2 , Pl 6 , Pl 7 , Pl 15 , and Pl 20 ), and 13 (Pl 5 , Pl 8 , and Pl 21 ) of the sunflower genome (Roeckel-Drevet et al. 1996;Vear et al. 1997;Gedil et al. 2001;Bert et al. 2001;Radwan et al. 2003;Dußle et al. 2004;Mulpuri et al. 2009;de Romano et al. 2010;Bachlava et al. 2011;Liu et al. 2012;Qi et al. 2015bQi et al. , 2016Ma et al. 2017;Zhang et al. 2017). Recently, Pecrix et al. (2018a, b) reported 11 new DM genes in sunflower. ...
The sunflower germplasm line TX16R is resistant to Plasmopara halstedii (causal agent of sunflower downy mildew) and Puccinia helianthi (causal agent of sunflower rust), which are two destructive foliar diseases in sunflower production worldwide. This study reports the mapping of the downy mildew and rust resistance genes Pl33 and R16 from TX16R, respectively. Progeny testing of test crosses for downy mildew resistance suggested that Pl33 localizes to linkage group (LG) 4 of the sunflower genome. Molecular mapping of Pl33 using simple sequence repeat (SSR) and single-nucleotide polymorphism (SNP) markers identified Pl33 cosegregating with ORS644, ORS963, SFW04901, and SFW04052, and linking to two SNPs, NSA_006089 and NSA_008496, at a genetic distance of 0.2 cM on the proximal side. Bulked segregant analysis using SSR and EST-SSR markers from LGs previously reported for rust genes identified polymorphic SSR markers associated with rust resistance on LG13. R16 was mapped between SFW08875 and SFW04317 on LG13, with a genetic distance of 1.8 and 1.1 cM, respectively. The 15 linked markers span a genetic distance of 27.4 cM in LG13. The cosegregating or closely linked markers to the two resistance genes will facilitate marker-assisted selection (MAS) and gene pyramiding, and will further assist in identifying genes responsible for DM and rust resistance.
... High levels of polymorphism have already been observed when the parental lines of crosses used to map resistance were of very different origins, with one parent from wild H. annuus ecotypes or from different Helianthus species. In the first report mapping Pl ARG , chromosome 1 appeared much shorter in a cross involving H. argophyllus and cultivated sunflower (Dussle et al., 2004) than in crosses between two cultivated sunflower lines (Wieckhorst et al., 2010). Moreover, it has recently been shown in rice that regions with high levels of polymorphism, in some cases associated with clusters of resistance genes, display reduced crossover frequencies (Mieulet et al., 2018); illustrating a negative correlation between genome divergence of the parental lines and recombination rate. ...
Resistance to downy mildew (Plasmopara halstedii) in sunflower (Helianthus annuus L.) is conferred by major resistance genes, denoted Pl. Twenty-two Pl genes have been identified and genetically mapped so far. However, over the past 50 years, wide-scale presence of only a few of them in sunflower crops led to the appearance of new, more virulent pathotypes (races) so it is important for sunflower varieties to carry as wide a range of resistance genes as possible. We analyzed phenotypically 12 novel resistant sources discovered in breeding pools derived from two wild Helianthus species and in eight wild H. annuus ecotypes. All were effective against at least 16 downy mildew pathotypes. We mapped their resistance genes on the sunflower reference genome of 3,600 Mb, in intervals that varied from 75 Kb to 32 Mb using an AXIOM® genotyping array of 49,449 SNP. Ten probably new genes were identified according to resistance spectrum, map position, hypersensitive response to the transient expression of a P. halstedii RXLR effector, or the ecotype/species from which they originated. The resistance source HAS6 was found to carry the first downy mildew resistance gene mapped on chromosome 11, whereas the other resistances were positioned on chromosomes 1, 2, 4, and 13 carrying already published Pl genes that we also mapped physically on the same reference genome. The new genes were designated Pl23–Pl32 according to the current nomenclature. However, since sunflower downy mildew resistance genes have not yet been sequenced, rules for designation are discussed. This is the first large scale physical mapping of both 10 new and 10 already reported downy mildew resistance genes in sunflower.
... Unlike, the Pl 8 gene, Pl Arg is not clustered. Several authors identified and developed different types of markers (SSRs, SNPs, RGCs) for MAS (Dußle et al., 2004;Wieckhorst et al., 2010;Imerovski et al., 2014b), some of these were also validated across a panel of sunflower lines. ORS716 was identified as the most useful marker in MAS (Table 1). ...
In sunflower, molecular markers for simple traits as, e.g., fertility restoration, high oleic acid content, herbicide tolerance or resistances to Plasmopara halstedii, Puccinia helianthi, or Orobanche cumana have been successfully used in marker-assisted breeding programs for years. However, agronomically important complex quantitative traits like yield, heterosis, drought tolerance, oil content or selection for disease resistance, e.g., against Sclerotinia sclerotiorum have been challenging and will require genome-wide approaches. Plant genetic resources for sunflower are being collected and conserved worldwide that represent valuable resources to study complex traits. Sunflower association panels provide the basis for genome-wide association studies, overcoming disadvantages of biparental populations. Advances in technologies and the availability of the sunflower genome sequence made novel approaches on the whole genome level possible. Genotype-by-sequencing, and whole genome sequencing based on next generation sequencing technologies facilitated the production of large amounts of SNP markers for high density maps as well as SNP arrays and allowed genome-wide association studies and genomic selection in sunflower. Genome wide or candidate gene based association studies have been performed for traits like branching, flowering time, resistance to Sclerotinia head and stalk rot. First steps in genomic selection with regard to hybrid performance and hybrid oil content have shown that genomic selection can successfully address complex quantitative traits in sunflower and will help to speed up sunflower breeding programs in the future. To make sunflower more competitive toward other oil crops higher levels of resistance against pathogens and better yield performance are required. In addition, optimizing plant architecture toward a more complex growth type for higher plant densities has the potential to considerably increase yields per hectare. Integrative approaches combining omic technologies (genomics, transcriptomics, proteomics, metabolomics and phenomics) using bioinformatic tools will facilitate the identification of target genes and markers for complex traits and will give a better insight into the mechanisms behind the traits.
... Based on the phenotypic evaluations and the scoring of disease symptoms on sunflower genotypes by Trakya Agricultural Research Institute, RHA-419, HA-R5 and P64LC53 were reported as resistant genotypes for Pl arg , Pl 13 , and Pl 8 , respectively. Moreover, RHA-419 and HA-R5 were reported by different studies to include Pl arg and Pl 13 , respectively (Dußle et al., 2004;Mulpuri et al., 2009;Qui et al., 2017). ...
Downy mildew is a fungal disease caused by Plasmopara halstedii and leads to loss of yield up to 100% in sunflower. Disease control is performed mostly through chemical seed treatment and breeding. Due to the time consuming nature of conventional breeding, it is supported by biotechnological approaches. Marker-assisted selection (MAS) is a strategic approach in molecular breeding using molecular markers. Single nucleotide polymorphisms (SNPs) such as insertions, deletions, and base-pair substitutions are more advantageous than other molecular markers. The abundance and biallelic nature of SNPs in a genome provide flexibility in the choosing of SNPs at the desired loci. Competitive allele-specific PCR (KASP) is a genotyping technology for screening of trait-specific SNP markers. In this study, SNP markers (NSA002867, NSA006138; NSA000052, NSA000354; NSA002220, NSA002251) linked with the downy mildew resistance genes Plarg,Pl13, and Pl8, respectively, were analyzed via KASP in three parental crosses (RHA-419 × Colombi, RHA-419 × P64LC53, RHA-419 × Oliva) for Plarg, one parental cross (HA-R5 × P64LC53) for Pl13, one parental cross (P64LC53 × HA-89) for Pl8, and 140 F2 individuals. According to the allelic discrimination results, NSA002867 and NSA006138 markers were discriminative in all crosses for Plarg, NSA000354 marker was discriminative for Pl13, and NSA002220 and NSA002251 markers were discriminative for Pl8. This study has revealed the potential use of SNP markers in combination with KASP assay for MAS studies, particularly downy mildew resistance in sunflower.
... Pl 6 and Pl 7 were both previously mapped to LG8 of the sunflower genome (Bouzidi et al., 2002;Gascuel et al., 2015), whereas Pl 8 was mapped to LG13 (Bachlava et al., 2011). Since Pl arg was mapped to LG1, different from all other Pl genes previously mapped using SSRs, it was concluded that Pl arg provides a new unique source of resistance to P. halstedii (Dußle et al., 2004;Wieckhorst et al., 2008). Hulke et al. (2010a) released three DM-resistant genetic stocks: HA 458 based on CWR H. annuus from Texas, HA 459 based on CWR H. annuus from Idaho, and HA 460 based on H. argophyllus from Texas, resistant to a composite of the most common and most virulent races of P. halstedii. ...
Sunflower (Helianthus annuus L.) is a relatively new crop among world field crops and is unique in several respects. It is one of only a few crops (cranberries, blueberries, and pecans are others) to have originated from the United States. Sunflower is further unique in that it has been bred for distinctly different uses: as an oilseed crop, for confection and birdseed uses, and, finally, as an ornamental for home gardens and a colorful array of sunflowers for the cut-flower industry. The following article will cover the history of the crop; botany of the genus Helianthus; US production practices, including pest problems, properties, and processing of sunflower oil; sunflower by-products; confectionery sunflower; and future trends.
... Pl 6 and Pl 7 were both previously mapped to LG8 of the sunflower genome (Bouzidi et al., 2002;Gascuel et al., 2015), whereas Pl 8 was mapped to LG13 (Bachlava et al., 2011). Since Pl arg was mapped to LG1, different from all other Pl genes previously mapped using SSRs, it was concluded that Pl arg provides a new unique source of resistance to P. halstedii (Dußle et al., 2004;Wieckhorst et al., 2008). Hulke et al. (2010a) released three DM-resistant genetic stocks: HA 458 based on CWR H. annuus from Texas, HA 459 based on CWR H. annuus from Idaho, and HA 460 based on H. argophyllus from Texas, resistant to a composite of the most common and most virulent races of P. halstedii. ...
Sunflower (Helianthus annuus L.) is one of the few crops native to the United States. The current USDA–ARS National Plant Germplasm System (NPGS) crop wild relatives sunflower collection is the largest extant collection in theworld, containing 2519 accessions comprising 53 species—39 perennial and 14 annual. To fully utilize gene bank collections, however, researchers need more detailed information about the amount and distribution of genetic diversity present within the collection. The wild species are adapted to a wide range of habitats and possess considerable variability for most biotic and abiotic traits. This represents a substantial amount of genetic diversity available for many agronomic traits for cultivated sunflower, which has a very narrow genetic base. Sunflower ranked fifth highest among 13 crops of major importance to global food security surveyed from the mid-1980s to 2005 in the use of traits from crop wild relatives. The estimated annual economic contribution of the wild species for cultivated sunflower is between US$267 to 384 million. Most of the value is derived from the PET1 cytoplasm from wild H. petiolaris, disease resistance genes, abiotic salt tolerance, and resistance to imidazolinone and sulfonylurea herbicides. Crop wild relatives provide a wide range of valuable attributes for traditional and molecular breeding, as well as for ecological experimentation, and have enabled rapid advances in ecological and evolutionary genetics. The wild species of Helianthus continue to contribute specific traits to combat emerging pests and environmental challenges and, at the same time, are preserved for future generations.
... The method was originally developed for mapping resistance gene from a wild germplasm source (gene Dm5/8 was introgressed in lettuce from the wild species L. serriola) (Michelmore et al., 1991). Examples of successful use of BSA for mapping gene from wild species are available in different crops, including wheat (Kang et al., 2012), rice (Chen et al., 2006), and sunflower Bouzidi et al., 2002;Radwan et al., 2003;Dußle et al., 2004;Wieckhorst et al. 2010). ...
Broomrape (Orobanche cumana Wallr.) is a parasitic plant that can cause significant yield losses in sunflower. Race composition in broomrape populations changes constantly, and novel resistance genes need to be discovered and introduced into sunflower. According to results of trials in fields where broomrape races E, F and G were detected, inbred line HA-267 has resistance gene higher than Or 6. This study showed that resistance in HA-267 is under the control of a single recessive gene. An attempt to map the resistance gene using bulk segregant analyses (BSA) did not give positive results, presumably due to a low level of polymorphism between the parental lines used for mapping population development. Screening of lines HA-98-PR, OD-DI-100 and OD-DI-82 was performed with SSR molecular markers, in order to select the most suitable one for mapping population development.
... Pl 6 and Pl 7 were both previously mapped to LG8 of the sunflower genome (Bouzidi et al., 2002;Gascuel et al., 2015), whereas Pl 8 was mapped to LG13 (Bachlava et al., 2011). Since Pl arg was mapped to LG1, different from all other Pl genes previously mapped using SSRs, it was concluded that Pl arg provides a new unique source of resistance to P. halstedii (Dußle et al., 2004;Wieckhorst et al., 2008). Hulke et al. (2010a) released three DM-resistant genetic stocks: HA 458 based on CWR H. annuus from Texas, HA 459 based on CWR H. annuus from Idaho, and HA 460 based on H. argophyllus from Texas, resistant to a composite of the most common and most virulent races of P. halstedii. ...
Sunflower (Helianthus annuus L.) is a relatively new crop among world field crops and is unique in several respects. It is one of only a few crops (cranberries, blueberries, and pecans are others) to have originated from the United States. Sunflower is further unique in that it has been bred for distinctly different uses: as an oilseed crop, for confection and birdseed uses, and, finally, as an ornamental for home gardens and a colorful array of sunflowers for the cut-flower industry. The following article will cover the history of the crop; botany of the genus Helianthus; US production practices, including pest problems, properties, and processing of sunflower oil; sunflower by-products; confectionery sunflower; and future trends.
... Chi-squared analysis indicated a segregation distortion in the F 2 population for R 14 , PHC, and ten of 14 linked molecular markers from an expected 1:2:1 or 3:1 ratio. A similar deviation was reported for Pl ARG , a sunflower downy mildew resistance gene derived from H. argophyllus Torrey and Gray (Dußle et al. 2004;Wieckhorst et al. 2010); for R 5 , a rust resistance gene derived from H. argophyllus (Qi et al. 2012a); and for Rf 6 , a sunflower male fertility restoration gene derived from H. angustifolius (Liu et al. 2013 percentage of homozygous individuals with resistance or Rf genes was detected for all these cases, indicating a low transmission rate of alien chromosome segments carrying the target genes into the cultivated sunflower, or the possible existence of genes affecting selfcompatibility which resulted in insufficient seeds for progeny test for some F 2 individuals. Several factors may cause segregation distortion, such as gametic selection, zygotic selection, interspecific sterility genes (S), and chromosome translocation (Lyttle 1991;Kumar et al. 2007;Gutiérrez et al. 2010;Liu et al. 2010). ...
Sunflower, the fifth largest oilseed crop in the world, plays an important role in human diets. Recently, sunflower production in North America has suffered serious yield losses from newly evolved races of sunflower rust (Puccinia helianthi Schwein.). The rust resistance gene, designated R
14
, in a germplasm line PH 3 originated from a wild Helianthus annuus L. population resistant to 11 rust races. PH 3 has seedling with an extraordinary purple hypocotyl color. The objectives of this study were to map both the R
14
rust resistance gene and the purple hypocotyl gene-designated PHC in PH 3, and to identify molecular markers for marker-assisted breeding for sunflower rust resistance. A set of 517 mapped SSR/InDel and four SNP markers was used to detect polymorphisms between the parents. Fourteen markers covering a genetic distance of 17.0 cM on linkage group (LG) 11 were linked to R
14
. R
14
was mapped to the middle of the LG, with a dominant SNP marker NSA_000064 as the closest marker at a distance of 0.7 cM, and another codominant marker ORS542 linked at 3.5 cM proximally. One dominant marker ZVG53 was linked on the distal side at 6.9 cM. The PHC gene was also linked to R
14
with a distance of 6.2 cM. Chi-squared analysis of the segregation ratios of R
14
, PHC, and ten linked markers indicated a deviation from an expected 1:2:1 or 3:1 ratio. The closely linked molecular or morphological markers could facilitate sunflower rust-resistant breeding and accelerate the development of rust-resistant hybrids.
Hybrid plants were obtained by crossing cultivated sunflower (Helianthus annuus L., 2n=2x=34) lineARM-243B and a wild Helianthus species [H. argophyllus; 2n=2x=34; HEL-153/83 (PI-649865)], using the latter as pollen parent. The wild Helianthus accession was selected for this study because of its short duration and short plant height compared to other accessions of H. argophyllus. Morphological and cytological analyses were carried out to confirm the hybrid nature of the F1 plants. The hybrids exhibited morphological features intermediate to both the parents for few attributes and more related to wild Helianthus species like leaf and stem pubescence, stem hairiness, flower colour, stem size, branching, disc floret pigmentation, plant height, seed size and seed shape etc. A reduction in pollen fertility (87.5%) was recorded in F1 plants as compared to both the parents. Meiotic analysis revealed a mixture of univalents, bivalents, trivalents and quadrivalents in all the pollen mother cells (PMCs) analysed. In addition to bivalents and univalents, a trivalent was also observed in few PMCs, indicating segmental homology between chromosomes. Frequently observed chromosome configurations in diakinensis were 15 II + 1 IV and 13 II + 2 IV. The results suggested that the species H. argophyllus and H. annuus differ by 1-2 translocations and 1-2 inversions. Results show that the wild species is compatible with cultivated sunflower and using H. argophyllus cultivated sunflower can be improved for biotic (downy mildew) and abiotic stresses (drought and salinity).
The oomycete pathogen Plasmopara halstedii responsible for sunflower downy mildew (DM), that is a significant and important disease that greatly affects the economy. As of now, there is no non-race-specific resistance for this disease and breeders are depended on race-specific resistance to control DM disease. On the other hand, using conventional breeding procedure introgression of the DM resistance genes is a long-term task due to the highly virulent and aggressive nature of the P. halstedii pathogen. Molecular markers that can be applied at the seedling stage, offers rapid response for selection with higher precision as well as a lower cost. There are currently 36 downy mildew resistance genes (R genes), designated as Pl (Pl1-Pl36, Plhra, and PlArg, in sunflowers, each with a unique linkage group (LGs). The availability of DM resistance genomic data of sunflower, related to Single Nucleotide Polymorphisms (SNP) based markers with mine allelic diversity maximize the opportunity of utilizing Marker assisted selection (MAS) techniques for downy mildew resistance breeding. This review highlights the available genetic marker and their utilization at MAS techniques for enhancing downy mildew disease resistant breeding program of sunflowers.
Key message
Two new downy mildew resistance genes, Pl37 and Pl38, were introgressed from wild sunflower species into cultivated sunflower and mapped to sunflower chromosomes 4 and 2, respectively
Abstract
Downy mildew (DM), caused by the oomycete pathogen Plasmopara halstedii (Farl.) Berl. & de Toni, is known as the most prevalent disease occurring in global sunflower production areas, especially in North America and Europe. In this study, we report the introgression and molecular mapping of two new DM resistance genes from wild sunflower species, Helianthus annuus and H. praecox, into cultivated sunflower. Two mapping populations were developed from the crosses of HA 89/H. annuus PI 435417 (Pop1) and CMS HA 89/H. praecox PRA-417 (Pop2). The phenotypic evaluation of DM resistance/susceptibility was conducted in the BC1F2-derived BC1F3 populations using P. halstedii race 734. The BC1F2 segregating Pop1 was genotyped using an Optimal GBS AgriSeq™ Panel consisting of 768 mapped SNP markers, while the BC1F2 segregating Pop2 was genotyped using a genotyping-by-sequencing approach. Linkage analysis and subsequent saturation mapping placed the DM resistance gene, designated Pl37, derived from H. annuus PI 435417 in a 1.6 cM genetic interval on sunflower chromosome 4. Pl37 co-segregated with SNP markers SPB0003 and C4_5738736. Similarly, linkage analysis and subsequent saturation mapping placed the DM resistance gene, designated Pl38, derived from H. praecox PRA-417 in a 0.8 cM genetic interval on sunflower chromosome 2. Pl38 co-segregated with seven SNP markers. Multi-pathotype tests revealed that lines with Pl37 or Pl38 are immune to the most prevalent and virulent P. halstedii races tested. Two germplasm lines, HA-DM15 with Pl37 and HA-DM16 with Pl38, were developed for use in sunflower DM-resistance breeding.
Rust and downy mildew (DM) are two important sunflower diseases that lead to significant yield losses globally. The use of resistant hybrids to control rust and DM in sunflower has a long history. The rust resistance genes, R13a and R16, were previously mapped to a 3.4 Mb region at the lower end of sunflower chromosome 13, while the DM resistance gene, Pl33, was previously mapped to a 4.2 Mb region located at the upper end of chromosome 4. High-resolution fine mapping was conducted using whole genome sequencing of HA-R6 (R13a) and TX16R (R16 and Pl33) and large segregated populations. R13a and R16 were fine mapped to a 0.48 cM region in chromosome 13 corresponding to a 790 kb physical interval on the XRQr1.0 genome assembly. Four disease defense-related genes with nucleotide-binding leucine-rich repeat (NLR) motifs were found in this region from XRQr1.0 gene annotation as candidate genes for R13a and R16. Pl33 was fine mapped to a 0.04 cM region in chromosome 4 corresponding to a 63 kb physical interval. One NLR gene, HanXRQChr04g0095641, was predicted as the candidate gene for Pl33. The diagnostic SNP markers developed for each gene in the current study will facilitate marker-assisted selections of resistance genes in sunflower breeding programs.
Sunflower, a relevant crop for oil production in temperature regions, is subjected to various biotic stresses. Significance of a particular stress agent, both spatially and temporally, is determined by the environmental limitations and the pest population variability. This chapter provides a review of the major sunflower diseases and pests, with an emphasis on their distribution and description of the damage they may cause. Besides, we discuss different strategies used in sunflower breeding for biotic stress resistance, strategy that is reliable, durable, cost effective and with low negative impact on environment, for pest and disease control. During a long history of sunflower cultivation, several major breakthroughs in breeding for resistance to diseases and pests were made. Recent breakthrough in sunflower genomics and availability of genome data of both sunflower and its pathogens opens up the new possibilities for introduction of biotic stress resistance into cultivated sunflower. In the light of changes made over the history and the recent findings we discuss new tools available for designing sunflower crop resilient to biotic stresses.Keywords
Helianthus annuus
Breeding for resistanceGenomicsDiseasesPestsBroomrape
Unlabelled:
Downy mildew (DM) is one of the most serious diseases in sunflower-growing regions worldwide, often significantly reducing sunflower yields. The causal agent of sunflower DM, the oomycete pathogen Plasmopara halstedii, is highly virulent and aggressive. Studying regional disease spread and virulence evolution in the DM pathogen population is important for the development of new sunflower inbred lines with resistance to the existing DM pathogen. The sunflower line 803-1, as one of nine international differential hosts, has been used in the identification of P. halstedii virulent pathotypes in sunflower since 2000. The DM resistance gene in 803-1 was temporally designated Pl5 + based on allelic analysis but has not been molecularly characterized. In the present study, bulked segregant analysis and genetic mapping confirmed the presence of the Pl gene within a large gene cluster on sunflower chromosome 13 in 803-1, as previously reported. Subsequent saturation mapping in the gene target region with single nucleotide polymorphism (SNP) markers placed this gene at an interval of 3.4 Mb in the XRQ reference genome assembly, a location different from that of Pl5. Therefore, the Pl gene in 803-1 was re-designated Pl36 because it is not allelic with Pl5. Four SNP markers co-segregated with Pl36, and SNP SFW05743 was 1.1 cM proximal to Pl36. The relationship of eight Pl genes in the cluster is discussed based on their origin, map position, and specificity of resistance/susceptibility to DM infection.
Supplementary information:
The online version contains supplementary material available at 10.1007/s11032-022-01280-1.
Increase in the food demand and unprecedented level of environmental stresses have created major challenges to ensure global food security. Under such circumstances, wild species of crops serve as a genetic reservoir to improve yield, quality and adaptability of modern cultivars. Previously reported work of the introduction of genes from wild to cultivated species has drawn the attention of plant scientists towards the role of wild species in crop improvement. Contemporary genomic tools can also be exploited to understand the genetic architecture and diversity of crop wild relatives for their efficient use in practical plant breeding. Considering the value of wild genetic resources in sustainable agriculture, numerous worldwide efforts have been made for its preservation. In view of its importance, this chapter is written on a broader prospective to highlight the utilization and conservation of crop wild germplasm.
The genus Gossypium is comprised of more than 50 genetically diverse species with different origins and ploidy levels. Each of cultivated and wild species is a source of unique alleles to improve cotton crop under ever increasing fiber demand and rapidly evolving climatic factors. Formerly, most of the improvement has been made in cotton germplasm by utilizing the genetic diversity of only cultivated types of species. The plenty of examples are reported for the utilization of wild cotton species in plant breeding despite of the fact of proven to be a novel genetic resource. The major hindrance was the transfer of genetic material which is now easier as compared to past due to advancement of gene transfer methods and technologies. Therefore, the conservation and utilization of cotton wild germplasm have gained much importance and is now become imperative to sustain the yield and quality of cotton fibers. This chapter highlights the background and potential of wild species of cotton to improve yield, quality, and adaptability of modern cultivars.
Harmful effects of climate change, human interference, and environmental stresses have opened new challenges for food security and natural variability. Like other crops, the domestication of barley has led toward a significant reduction in genetic diversity and created hurdles to develop well-adapted cultivars. One of the best solutions toward these challenges is the exploitation of crop wild germplasm that niche in extreme geographical locations. Wild progenitors have potential to transfer adaptation loci in modern cultivars, which will make them fit for changing climate. Wild barley could be the potential source for genetic variability and increasing capability to withstand against biotic and abiotic stress factors and can be collected from its natural area of distribution, especially from the Mediterranean region. In this chapter, we have highlighted the significance of wild germplasm of barley and adaptive genes they have for various biotic and abiotic stress resistance/tolerance.
Due to the rapid increase in the human population, enough food production for all humankind will be a serious problem in the future. The higher yielding cultivars as well as advanced cultivation techniques combining with these varieties are the most proper solution to reduce hunger and to feed the world. New variety development with new yield and stress tolerant traits could be possible mostly from utilizing the new genetic resources. The complex of cultivated sunflower Helianthus annuus L. and its relatives of the same genus is an appropriate model for using the genetic diversity of wild Helianthus species for developing new sunflower genotypes. Until today, many new sunflower varieties have been created based on the use of wild germplasm.
Downy mildew (DM) is one of the severe biotic threats to sunflower production worldwide. The inciting pathogen, Plasmopara halstedii, could overwinter in the field for years, creating a persistent threat to sunflower. The dominant genes Pl18 and Pl20 conferring resistance to known DM races have been previously mapped to 1.5 and 1.8 cM intervals on sunflower chromosomes 2 and 8, respectively. Utilizing a whole-genome resequencing strategy combined with reference sequence-based chromosome walking and high-density mapping in the present study, Pl18 was placed in a 0.7 cM interval on chromosome 2. A candidate gene HanXRQChr02g0048181 for Pl18 was identified from the XRQ reference genome and predicted to encode a protein with typical NLR domains for disease resistance. The Pl20 gene was placed in a 0.2 cM interval on chromosome 8. The putative gene with the NLR domain for Pl20, HanXRQChr08g0210051, was identified within the Pl20 interval. SNP markers closely linked to Pl18 and Pl20 were evaluated with 96 diverse sunflower lines, and a total of 13 diagnostic markers for Pl18 and four for Pl20 were identified. These markers will facilitate to transfer these new genes to elite sunflower lines and to pyramid these genes with broad-spectrum DM resistance in sunflower breeding.
One of the most dangerous diseases on sunflower is downy mildew caused by oomycete Plasmopara halstedii. Introduction of dominant genes of resistance to this pathogen into a host-plant is the most effective economic and ecologically safe method of this pathogen control. The current DNA-technologies allow controlling these genes presence at the any stage of breeding. Currently, the genes Pl6, Pl13 and Plarg are the most effective ones controlling resistance to the most races of P. halstedii. We approbated known from the literary sources two STS and two SSR-markers of these genes on the lines and breeding samples. Three studied molecular markers – HаP3 (locus Pl6), ORS1008 (locus Pl13) and ORS509 (locus Plarg) – allowed us identifying the mentions genes in lines and breeding samples of VNIIMK. The studied DNA-markers can be interested in marker-associated sunflower breeding on resistance to a downy mildew pathogen.
Downy mildew, caused by Plasmopara halstedii (Farl.) Berl. and de Toni, is an economically important disease in cultivated sunflowers, Helianthus annuus L. Resistance genes incorporated into commercial hybrids are used as an effective disease management tool, but the duration of effectiveness is limited as virulence evolves in the pathogen population. A comprehensive assessment of pathogen virulence was conducted in 2014 and 2015 in the U.S. Great Plains states of North Dakota and South Dakota, where approximately 75% of the U.S. sunflower is produced annually. The virulence phenotypes (and races) of 185 isolates were determined using the U.S. standard set of nine differentials. Additionally, the virulence phenotypes of 61 to 185 isolates were determined on 13 additional lines that have been used to evaluate pathogen virulence in North America and/or internationally. Although widespread virulence was identified on several genes, new virulence was identified on the Pl
8
resistance gene, and no virulence was observed on the Pl
Arg
, Pl
15
, Pl
17
and Pl
18
genes. Results of this study suggest that three additional lines should be used as differentials and agree with previous studies that six lines proposed as differentials should be used in two internationally accepted differential sets. For effective disease management using genetic resistance, it is critical that virulence data be relevant and timely. This is best accomplished when pathogen virulence is determined frequently and by using genetic lines containing resistance genes actively incorporated into commercial cultivars.
Sunflower (Helianthus annuus L.) is one of the most important vegetable oil sources in the world and in Turkey. The preference of sunflower oil in the consumption of vegetable oil increases the importance of sunflower in Turkey. Fungal diseases are the most important limiting factors sunflower yield and oil content in sunflower production and downy mildew which is caused by the Plasmopara halstedii (Farl.) Berl. and de Toni leads until 100% yield loses. Therefore, development and the use of resistant varieties in sunflower production in Turkey help to reduce yield loses in sunflower. Several downy mildew resistance genes (Pl) have been identified and used in breeding for resistance cultivars. However, developing resistant varieties by classical breeding is a longer, costly and harder way and utilizing biotechnological methods and marker assistant selection (MAS) give to opportunity to accelerate the process with giving efficient and confident selection. In this study, it was aimed that to determine suitable molecular markers which will be used possibly in the selection related to Pl6 and PlArg genes conferring effective resistance against to virulent strains in Trakya region. Parents and 120 individuals at BC4 breeding level (Pl6 and PlArg genes sources were crossed with susceptible sunflower varieties) were used for molecular marker studies. All plant materials were also screened phenotypically by inoculation with pathogen spores. As results, two markers for Pl6 gene were detected as useful for MAS but no any suitable markers were found to detect PlArg gene among used markers in this and previous studies.
Sunflower is well known as an important oilseed crop for the consumers, and consumed as roasted, confectionary and bird feed seed. The plant has been subjected to the improvement by plant breeders which caused yellow revolution in many countries of the world. Russian Plant breeders improved its seed oil contents which converted this crop from a roadside plant to world famous oilseed crop. The cultivated germplasm retained 50% of genetic diversity present in crop wild relative. This may be threatened due to worldwide hybrid cultivation which share common parentage and source of cytoplasmic male sterility. Therefore, there is a need to use the available genetic diversity within cultivated and wild germplasm to develop pre breeding lines and elite breeding material with good combining ability. Sunflower breeding revolves around the development of breeding lines suitable for hybrid breeding, diseases, abiotic stress and herbicide resistance. These objectives were fulfilled by recurrent selection for population improvement. Wide crosses were made to transfer cytoplasmic male sterility, diseases, abiotic and orobanche resistance. Moreover, induced mutations were used to induce new genetic variability for diseases and herbicide resistance and reduction of plant height. Marker- assisted- selection has been validated for rust resistance, downey mildew resistance, oleic acid contents, and fertility restorer genes. Transgenic sunflower development could be used to enhance oil content and quality. Sunflower breeding will be greatly facilitated by the genomic tools such as CRISPR/Cas and whole genome association mapping.
Simple sequence repeats (SSR) polymorphism of 34 microsatellite loci (LG1, 8 and 13) was studied in lines carrying the downy mildew resistance genes Pl and lines with no Pl . The microsatellite loci ORS328 and ORS781 were selected as markers for genes Pl6 and Pl8 in lines HA 335 and QHP-1, respectively. Markers were identified for gene Pl ARG in RHA 419 and some accessions of H. argophyllus . The SSR markers ORS509, ORS605, ORS610, ORS1182 and ORS1039 were proven to reliably identify the parental line carrying Pl ARG gene, control and select the heterozygous F 1 hybrids and identify homozygous genotypes in F 2 generations. Obtained results indicate the necessity of validation of the markers in various germplasm pools and breeding collections. The SSR markers that are tightly linked to Pl 6 , Pl 8 , Pl ARG would be useful in the sunflower breeding. Pl ARG homozygous F 2 segregants, developed and identified with marker assisted selection in this study, are recommended for further breeding as a new source of genetically determined resistance to downy mildew.
Sclerotinia head and stalk rots are among the most devastating diseases in sunflower (Helianthus annuus L.). Breeding for resistance to these diseases while maintaining or improving yield and quality is complicated by the quantitative inheritance of the resistance, for which there are few genes of major effect. The objective of this work was to provide new diversity to sunflower breeding organizations for yield and Sclerotinia resistance, together with other useful agronomic and end user traits. Four restorer germplasms, RHA 461 (Reg. No. GP-337, PI 655012), RHA 462 (Reg. No. GP- 338; PI 655013), RHA 463 (Reg. No. GP-339; PI 655014), and RHA 468 (Reg. No. GP-341; PI 667184), and three maintainer germplasms, HA 465 (Reg. No. GP-342; PI 670488), HA 466 (Reg. No. GP-340; PI 667183), and HA 467 (Reg. No. GP- 343; PI 670489) were developed by the USDA-ARS and the North Dakota Agricultural Experiment Station, Fargo, ND. Testcrosses with these germplasms had yield similar to highyielding commercial checks and Sclerotinia resistance similar to the highly resistant check ‘Northrup King 277'. Some of the lines also have high oleic acid in the seed oil, downy mildew resistance, and tolerance to imidazolinone herbicides. The lines are available for sunflower breeders to integrate into their breeding programs for additional diversity.
Key message:
Genotyping-by-sequencing revealed a new downy mildew resistance gene, Pl 20 , from wild Helianthus argophyllus located on linkage group 8 of the sunflower genome and closely linked to SNP markers that facilitate the marker-assisted selection of resistance genes. Downy mildew (DM), caused by Plasmopara halstedii, is one of the most devastating and yield-limiting diseases of sunflower. Downy mildew resistance identified in wild Helianthus argophyllus accession PI 494578 was determined to be effective against the predominant and virulent races of P. halstedii occurring in the United States. The evaluation of 114 BC1F2:3 families derived from the cross between HA 89 and PI 494578 against P. halstedii race 734 revealed that single dominant gene controls downy mildew resistance in the population. Genotyping-by-sequencing analysis conducted in the BC1F2 population indicated that the DM resistance gene derived from wild H. argophyllus PI 494578 is located on the upper end of the linkage group (LG) 8 of the sunflower genome, as was determined single nucleotide polymorphism (SNP) markers associated with DM resistance. Analysis of 11 additional SNP markers previously mapped to this region revealed that the resistance gene, named Pl 20 , co-segregated with four markers, SFW02745, SFW09076, S8_11272025, and S8_11272046, and is flanked by SFW04358 and S8_100385559 at an interval of 1.8 cM. The newly discovered P. halstedii resistance gene has been introgressed from wild species into cultivated sunflower to provide a novel gene with DM resistance. The homozygous resistant individuals were selected from BC2F2 progenies with the use of markers linked to the Pl 20 gene, and these lines should benefit the sunflower community for Helianthus improvement.
The sunflower plant has a sun-like beautiful flower and is one of the most important oilseed crops in the world. Sunflower oil is premium cooking oil, one of the major vegetable oils, and can be used as a “biodiesel” fuel. Sunflower seeds are used as a food additive, a confection for snack foods, and bird foods. Additionally, sunflower has potential to be an alternative producer of rubber. Although there is no genetically modified sunflower product on the market yet, biotechnology is impacting sunflower development and production. In the past several years, remarkable progress has been made in the efforts of generating novel sunflower products. We summarize the advances in genetic transformation, discovery of trait genes and promoters, applications of biotechnology in improving various input agronomic and output quality traits, and biosafety in sunflower.
Evaluation of sunflower germplasm for downy mildew resistance is an integral part of both public and private breeding programs. Testing methods were developed decades ago and are described in many languages in many different journals, as well as being passed on from person to person by word of mouth. Many people, if fact, dismiss downy mildew testing as a "cookbook" technique that can be delegated to the least trained person in the organization and still have satisfactory results. When downy mildew evaluations are "working," it is true that the procedures are simple. When the evaluations produce unsatisfactory results, then it is time to reexamine each step of the procedure, in detail, to see where the problem(s) may have occurred. The purpose of this review is to examine the downy mildew evaluation procedure step-by-step and to explain the optimum conditions. The text of the review is intentionally not technical and no references nor data will be included. Some of the information may seem extremely rudimentary, but it may be wiser to cover even the smallest detail rather than assume something that may, in time, prove crucial when overlooked. RULE #1: START WITH GOOD SEEDLINGS In order to insure that seedlings are clean, the seeds should be soaked in a 20% solution of household bleach. In the U.S., household bleach commonly contains 5.25% sodium hypochlorite, so a 20% solution will contain about 1% sodium hypochlorite. The bleach solution should also have a small amount of dish detergent in it, which will help to wet the waxy hulls. Additionally, if a large quantity of seeds is being sterilized, it is a good practice to cover the seeds with some object (dish, jar lid, etc.) in order to completely submerge the seeds in the bleach solution. We have found that 4-5 oz., plastic specimen cups, with tapered sides (SOLO or other brand), are a convenient size to hold 30-100 seeds, and are cheap enough to be disposable, yet sturdy enough to be reused many times. The identity of each seed lot should be written on a small paper label, in pencil or a bleach-resistant ink, and the label placed with the seeds in the bleach solution. Seeds produced under bags potentially have more fungal contamination than open-pollinated seeds, so soaking the seeds for two to ten minutes is advisable, and will do no harm. One may also wish to stir the seeds during this period to insure that all seeds are uniformly sterilized. We have soaked seeds in a 20% bleach solution up to 45 minutes with no effect on seed germination. After the bleach soak, seeds should be thoroughly rinsed under running tap water in a small household strainer. When there is no trace of soap bubbles left, one can assume that the bleach has also been completely removed. If quicker seed germination is desired, we have found that soaking seeds after
The Pl1 locus in sunflower, Helianthus annuus L., conferring resistance to downy mildew, Plasmopara halstedii, race 1 has been located in linkage group 1 of the consensus RFLP map of the cultivated sunflower. Bulked segregant analyses were used on 135 plants of an F2 progeny from a cross between a downy mildew susceptible line, GH, and RHA266, a line carrying Pl1. Two RFLP markers and one RAPD marker linked to the Pl1 locus have been identified. The RFLP markers are located at 5.6 cM and 7.1 cM on either side of Pl1. The RAPD marker is situated at 43.7 cM from Pl1. The significance and applications of these markers in sunflower breeding are discussed.
The density and utility of the molecular genetic linkage map of cultivated sunflower (Helianthus annuus L.) has been greatly increased by the development and mapping of several hundred simple sequence repeat (SSR) markers. Of 1089 public SSR markers described thus far, 408 have been mapped in a recombinant inbred line (RIL) mapping population (RHA280 × RHA801). The goal of the present research was to increase the density of the sunflower map by constructing a new RIL map (PHA × PHB) based on SSRs, adding loci for newly developed SSR markers to the RHA280 × RHA801 RIL map, and integrating the restriction fragment length polymorphism (RFLP) and SSR maps of sunflower. The latter was accomplished by adding 120 SSR marker loci to a backbone of 80 RFLP marker loci on the HA370 × HA372 F2 map. The map spanned 1275.4 centimorgans (cM) and had a mean density of 6.3 cM per locus. The PHA × PHB SSR map was constructed from 264 SSR marker loci, spanned 1199.4 cM, and had a mean density of 4.5 cM per locus. The RHA280 × RHA801 map was constructed by adding 118 new SSR and insertion-deletion (INDEL) marker loci to 459 previously mapped SSR marker loci. The 577-locus map spanned 1423.0 cM and had a mean density of 2.5 cM per locus. The three maps were constructed from 1044 DNA marker loci (701 unique SSR and 89 unique RFLP or INDEL marker loci) and supply a dense genomewide framework of sequence-based DNA markers for molecular breeding and genomics research in sunflower.
High-precision genetic mapping was used to define the regions that contain centromere functions on each natural chromosome
inArabidopsis thaliana. These regions exhibited dramatic recombinational repression and contained complex DNA surrounding large arrays of 180–base
pair repeats. Unexpectedly, the DNA within the centromeres was not merely structural but also encoded several expressed genes.
The regions flanking the centromeres were densely populated by repetitive elements yet experienced normal levels of recombination.
The genetically defined centromeres were well conserved among Arabidopsis ecotypes but displayed limited sequence homology between different chromosomes, excluding repetitive DNA. This investigation
provides a platform for dissecting the role of individual sequences in centromeres in higher eukaryotes.
These studies were undertaken to determine whether downy mildew resistance genes in sunflower were independent as first reported,
or linked as suggested by more recent hypotheses. The segregations for downy mildew reaction of 111 F3 progenies from a cross between a susceptible line and a line with Pl2 were used to locate this gene on the sunflower consensus RFLP linkage map. It was shown that Pl2 was linked to the same RFLP markers on linkage group 1 as Pl1 and Pl6, mapped earlier, and at a very similar distance. The F3 progenies showed exactly the same segregation patterns when tested with race 1 and race D. One hundred and fifty four progenies
from a cross between a susceptible line and HA335, containing Pl6 (considered as giving resistance to all Plasmopara halstedii races), were tested with the five French downy mildew races, 1, A, B, C and D. Two progenies were observed to show segregation
for races 1 and D, while appearing homozygous-resistant to races A , B and C. Tests on F4 progenies confirmed this separation of resistances with fixation of susceptibility to races 1 and D and resistance to races
A, B and C. It is concluded that the Pl6 gene is not a “strong” gene, giving resistance to all downy mildew races, but rather a cluster of genes, each providing resistance
to one, or a few, downy mildew races. The genes giving resistance to races 1 and D, on one hand, and to races A, B and C,
on the other hand, must be very closely linked, with about 0.6 cM between the two groups.
The Pl6 locus in the inbred sunflower (Helianthus annuus L.) line HA335 giving resistance to French races of downy mildew (Plasmopara halstedii (Farl.) Berl. & de Toni. was localized by molecular techniques. A bulked segregant analysis was made on the F2 progeny from a cross between this line and H52, a downy mildew susceptible line. The resistance gene in HA335 was found to have the same linked RFLP marker loci as those determined for Pl1 (resistance to race 1 in the line RHA266) on linkage group 1 of the consensus RFLP map of the cultivated sunflower. Pl1 and Pl6 thus appear either to be allelic or closely linked. The implications for sunflower breeding are discussed.
A sunflower line, XRQ, carrying the gene Pl5, which gives resistance to all French downy mildew races shows cotyledon-limited sporulation in seedling immersion tests;
consequently, segregations in crosses with other downy mildew resistance sources were tested both by this method and by a
secondary infection on leaves. Pl5 was found to segregate independently of Pl7 (HA338) but to be closely linked, or allelic, with Pl8 (RHA340). F3 and F4 progenies from a cross with a line containing Pl2 showed that Pl5 carries resistance to race 100 which segregates independently of Pl2. The Pl5 gene was mapped on linkage group 6 of the Cartisol RFLP map, linked to two RFLP markers, ten AFLP markers and the restorer
gene Rf1. Tests with downy mildew race 330 distinguished Pl5 and Pl8, the first being susceptible, the second resistant, whereas both these genes were active against race 304 to which Pl6 (HA335) and Pl7 gave susceptibility. It is concluded that Pl5 and Pl8 are closely linked on linkage group 6 and form a separate resistance gene group from Pl6/Pl7 on linkage group 1. The origins of these groups of downy mildew resistance genes and their use in breeding are discussed.
Several independent molecular genetic linkage maps of varying density and completeness have been constructed for cultivated
sunflower (Helianthus annuus L.). Because of the dearth of sequence and probe-specific DNA markers in the public domain, the various genetic maps of sunflower
have not been integrated and a single reference map has not emerged. Moreover, comparisons between maps have been confounded
by multiple linkage group nomenclatures and the lack of common DNA markers. The goal of the present research was to construct
a dense molecular genetic linkage map for sunflower using simple sequence repeat (SSR) markers. First, 879 SSR markers were
developed by identifying 1,093 unique SSR sequences in the DNA sequences of 2,033 clones isolated from genomic DNA libraries
enriched for (AC)n or (AG)n and screening 1,000 SSR primer pairs; 579 of the newly developed SSR markers (65.9% of the total) were polymorphic among
four elite inbred lines (RHA280, RHA801, PHA and PHB). The genetic map was constructed using 94 RHA280 × RHA801 F7 recombinant inbred lines (RILs) and 408 polymorphic SSR markers (462 SSR marker loci segregated in the mapping population).
Of the latter, 459 coalesced into 17 linkage groups presumably corresponding to the 17 chromosomes in the haploid sunflower
genome (x = 17). The map was 1,368.3-cM long and had a mean density of 3.1cM per locus. The SSR markers described herein supply a
critical mass of DNA markers for constructing genetic maps of sunflower and create the basis for unifying and cross-referencing
the multitude of genetic maps developed for wild and cultivated sunflowers.
Microsatellite Simple sequence repeat Helianthus Sunflower
A map of the sunflower genome, based on expressed sequences and consisting of 273 loci, was constructed. The map incorporates
data from seven F2 populations, for a total of 1115 individuals. Two hundred and fourty five loci corresponding to 170 anonymous cDNA markers
and four loci for morphological markers were mapped. We also mapped 18 loci corresponding to previously described genes or
to sequences obtained through homology cloning. The unit maps vary from 774 cM to 1060 cM, with an average value of 14 major
linkage groups. The integrated map is arranged in 17 major linkage groups including 238 loci, plus four small segments with
2–5 marker loci; and covers 1573 cM with an overall average marker interval of 7 cM. Thirty five percent of the markers were
dominant in nature and 30% showed inter-linkage group duplication without any indication of homoeologous linkage groups. Evidence
is provided for the independence of two distinct fertility restoration genes, for the presence of two loosely linked branching
loci, and for marker tightly linked to the Rf1 restoration locus. This map provides an efficient tool in breeding applications such as disease-resistance mapping, QTL analyses
and marker-assisted selection.
The barley mosaic virus complex has become one of the major pathogens of cultivated winter barley in central Europe. One resistance gene (ym4) mediates complete immunity against barley mild mosaic virus (BaMMV) and barley yellow mosaic virus type 1 (BaYMV-1). An attempt is made to molecularly characterize the ym4 resistance locus on the long arm of barley chromosome 3 by means of RFLP and sequence-tagged-site (STS) markers. Two closely linked molecular markers have been identified which are suitable for marker-assisted selection for the resistance gene. A high resolution mapping population is being developed in order to provide the basis for positional cloning of the ym4 resistance gene.
We developed bulked segregant analysis as a method for rapidly identifying markers linked to any specific gene or genomic region. Two bulked DNA samples are generated from a segregating population from a single cross. Each pool, or bulk, contains individuals that are identical for a particular trait or genomic region but arbitrary at all unlinked regions. The two bulks are therefore genetically dissimilar in the selected region but seemingly heterozygous at all other regions. The two bulks can be made for any genomic region and from any segregating population. The bulks are screened for differences using restriction fragment length polymorphism probes or random amplified polymorphic DNA primers. We have used bulked segregant analysis to identify three random amplified polymorphic DNA markers in lettuce linked to a gene for resistance to downy mildew. We showed that markers can be reliably identified in a 25-centimorgan window on either side of the targeted locus. Bulked segregant analysis has several advantages over the use of near-isogenic lines to identify markers in specific regions of the genome. Genetic walking will be possible by multiple rounds of bulked segregation analysis; each new pair of bulks will differ at a locus identified in the previous round of analysis. This approach will have widespread application both in those species where selfing is possible and in those that are obligatorily outbreeding.
Powdery mildew of barley, caused by Erysiphe graminis f. sp. hordei, is a model system for investigating the mechanism of gene-for-gene interaction between large-genome cereals and obligate-fungal pathogens. A large number of loci that confer resistance to this disease are located on the short arm of chromosome 5(1H). The Mla resistance-gene cluster is positioned near the telomeric end of this chromosome arm. AFLP-, RAPD-, and RFLP-derived markers were used to saturate the Mla region in a high-resolution recombinant population segregating for the (Mla6 + Mla14) and (Mla13 + Ml-Ru3) resistance specificities. These tightly linked genetic markers were used to identify and develop a physical contig of YAC and BAC clones spanning the Mla cluster. Three distinct NBS-LRR resistance-gene homologue (RGH) families were revealed via computational analysis of low-pass and BAC-end sequence data derived from Mla-spanning clones. Genetic and physical mapping delimited the Mla-associated, NBS-LRR gene families to a 240-kb interval. Recombination within the RGH families was at least 10-fold less frequent than between markers directly adjacent to the Mla cluster.
F(1) hybrids between the cultivated tomato (Lycopersicon esculentum) and the wild nightshade Solanum lycopersicoides are male sterile and unilaterally incompatible, breeding barriers that impede further crosses to tomato. Meiosis is disrupted in 2x hybrids, with reduced chiasma formation and frequent univalents, but is normal in allotetraploid hybrids, indicating the genomes are homeologous. In this study, a partially male-fertile F(1) was backcrossed to tomato, producing the first BC(1) population suitable for genetic mapping from this cross. BC(1) plants were genotyped at marker loci to study the transmission of wild alleles and to measure rates of homeologous recombination. The pattern of segregation distortion, in favor of homozygotes on chromosomes 2 and 5 and heterozygotes on chromosomes 6 and 9, suggested linkage to a small number of loci under selection on each chromosome. Genome ratios nonetheless fit Mendelian expectations. Resulting genetic maps were essentially colinear with existing tomato maps but showed an overall reduction in recombination of approximately 27%. Recombination suppression was observed for all chromosomes except 9 and 12, affected both proximal and distal regions, and was most severe on chromosome 10 (70% reduction). Recombination between markers on the long arm of this chromosome was completely eliminated, suggesting a lack of colinearity between S. lycopersicoides and L. esculentum homeologues in this region. Results are discussed with respect to phylogenetic relationships between the species and their potential use for studies of homeologous pairing and recombination in a diploid plant genome.
Resistance of sunflower to the obligate parasite Plasmopara halstedii is conferred by specific dominant genes, denoted Pl. The Pl6 locus confers resistance to all races of P. halstedii except one, and must contain at least 11 tightly linked genes each giving resistance to different downy mildew races. Specific primers were designed and used to amplify 13 markers covering a genetic distance of about 3 cM centred on the Pl6 locus. Cloning and sequence analysis of these 13 markers indicate that Pl6 contains conserved genes belonging to the TIR-NBS-LRR class of plant resistance genes.
The resistance of sunflower, Helianthus annuus L., to downy mildew, caused by Plasmopara halstedii, is conferred by major genes denoted by Pl. Using degenerate and specific primers, 16 different resistance gene analogs (RGAs) have been cloned and sequenced. Sequence comparison and Southern-blot analysis distinguished six classes of RGA. Two of these classes correspond to TIR-NBS-LRR sequences while the remaining four classes correspond to the non-TIR-NBS-LRR type of resistance genes. The genetic mapping of these RGAs on two segregating F2 populations showed that the non-TIR-NBS-LRR RGAs are clustered and linked to the Pl5/ Pl8 locus for resistance to downy mildew in sunflower. These and other results indicate that different Pl loci conferring resistance to the same pathogen races may contain different sequences.
This paper provides the first description of a consensus map of the cultivated sunflower genome (Helianthus annuus L., n=17 chromosomes), based on RFLP. A total of 180 probe-enzyme combinations were mapped on at least one of five segregating progenies (three F2 and two BC1 populations), revealing 237 loci that did not show any distortion of segregation. The consensus linkage map obtained with these loci covers 1150 cM and consists of 16 linkage groups of more than 20 cM, 7 groups of less than 20 cM and 18 unlinked loci. The mean distance between loci is 7 cM, but in some regions intervals of 20 cM remain. Genotypic and gametic segregation distortions affect about 7% of loci. It was found that 25% of the probes mapped using several different restriction enzymes or that on different progenies they revealed 2 or more loci.
Race 4 of downy mildew, incited by Plasmopara halstedii (Farl.) Berl. & de Toni, was first reported in sunflower (Helianthus annuus L) in the USA during 1985. Resistance to this race was found in lines derived from interspecific crosses of cultivated sunflower with three species of wild sunflower. The objectives of this investigation were to determine the genetic control of resistance found in the interspecific crosses and to determine if this resistance was conditioned by the same or different genes. Ratios tested utilizing a chisquare analysis for goodness of fit for F 2 and BC 1 F 1 generations indicated that resistance to Race 4 was conditioned by a single, dominant gene in all sources
Histopathological studies of the infection of sunflower seedlings by downy mildew (Plasmopara halstedii) have shown that penetration of roots and the lower part of the hypocotyl occurs for both compatible combinations (suseptibility) and incompatible combinations (resistance). After penetrating susceptible genotypes, the parasite develops intercellular hyphae and intracellular haustoria, leading to systemic invasion. In contrast, in resistant plants, as soon as colonization develops, hypersensitive-like reactions occur in the parenchyma, with the appearance of necrotic zones surrounded by dividing cells. Growth of the parasite is strongly inhibited and most hyphae are blocked before they reach the cotyledonary node.
Study of resistance of sunflower, Helianthus annuus L., to downy mildew, Plasmopara halstedii, shows that both susceptible and resistant seedlings are always infected by the fungus, then hypersensitive-like reactions occur in the parenchyma and necroses form around the parasite. Comparison of 21 incompatible combinations (resistance) shows that the extent of the fungus growth differs according to the host-race combination. With type I resistance, the fungus is limited to the roots andthe lower part of the hypocotyl. With the type II resistance, the fungus grows throughout the whole length of the hypocotyl and may sporulate on the cotyledons.
Sunflower downy mildew (SDM) caused by Plasmopara halstedii, is a major disease of sunflower. Eleven resistance genes have been identified, but allelic relationships among these genes are not clear. This study examined the inheritance and allelic relationships of genes conferring resistance to SDM races 1, 2 and 3 (virulence phenotypes 100, 300 and 700, respectively) and confirmed a twelfth resistance gene. Three USDA Plant Introductions, AMES 3235, PI 497250, and PI 497938, and three released lines, RHA 266, RHA 274 and DM-2 were studied. RHA 266 has only the Pl1 gene for race 1 resistance. Digenic inheritance of resistance was found in AMES 3235, PI 497250, and RHA 274. These lines have the Pl1 and Pl12 genes, conferring resistance to race 1, and the Pl2 and Pl11 genes, conferring resistance to race 2. DM-2 and PI 497938 have Pl12 (but not Pl1) for resistance to race 1, the Pl12 gene (but not the Pl2) for resistance to race 2, and Pl5 for resistance to race 3. These resistance genes will serve as a foundation for future gene designations and genetic diversity studies of resistance to SDM.
The proportion of loci deviating from the expected monogenic segregation ratios in the genera Lens. Capsicum, and Lycopersicon is significantly higher (61/114 genes, 54%) for progeny of interspecific hybrids than for progeny of intraspecific hybrids (7/52 genes, 13%). Although aberrant segregations are expected to be more common in progeny of interspecific hybrids, this is the first estimate of the magnitude of this phenomenon, based on a random sample of genes in a number of plant genera. We interpret these unequal segregations as the result of linkage between the markers and gene(s) that operate in pre- and postzygotic phases of reproduction. Such unequal segregations should be considered in planning breeding programs.
Sunflower (Helianthus annuus L.) production is endangered by several diseases, necessitating sophisticated disease management strategies. Downy mildew of sunflower, incited by Plasmopara halstedii (Farl.) Berl. et de Toni, is a major sunflower disease. Recent reports of pathotypes resistant to metalaxyl [N-(2,6-dimethylphenyl)-N-(methoxyacetyl)-DL-alanine methyl ester], which was used as a seed treatment against downy mildew, showed the necessity to breed for durable downy mildew resistance in future hybrids. This process can be accelerated by marker assisted selection (MAS) including pyramiding of several resistance genes. The objective of this study was to develop molecular markers for the Pl2 gene of cultivated sunflower, which confers resistance to downy mildew races 1, 2, 7, and 9. Two sets of near isogenic lines (AS110/AS110Pl2 and S1358/S1358Pl2) and bulks of a segregating F2 population were used to identify random amplified polymorphic DNA (RAPD) and amplified fragment length polymorphism (AFLP) markers. Public maintainer and restorer lines were used to evaluate the markers. Disease resistance was evaluated by the whole seedling immersion method. DNA was extracted from leaves at flowering. RAPD markers OPAA14750 and OPAC20831, as well as the AFLP marker E35M48-3, showed a tight linkage of about 2 centimorgans (cM) to the Pl2 locus. RAPD marker OPAA111008 linked to a distance of about 6 cM with the resistance locus and could be converted to a SCAR marker. Closely linked RAPDs and the sequence characterized amplified region (SCAR) marker demonstrated their practicability for marker assisted breeding by differentiating between resistant and susceptible germplasm of a set of diverse sunflower inbred lines.
A computerized procedure to construct integrated genetic maps is presented. The computer program (Join Map) can handle raw data from F 2 s, backcrosses and recombinant inbred lines, as well as listed pair‐wise recombination frequencies. The procedure is useful for combining linkage data that have been collected in different experiments; the result is a mathematical alignment of the distinct genetic maps. Data from single experiments can be dealt with as well. In view of the fast growing amount of linkage information for molecular markers, which is often being generated by different research groups, integrated maps provide useful information on the map position of genes and DNA markers.
The procedure performs a sequential build‐up of the map and, at each step, a numerical search for the best fitting order of markers. Weighted least squares is used for the estimation of map distances.
The articles published by the Annals of Eugenics (1925–1954) have been made available online as an historical archive intended for scholarly use. The work of eugenicists was often pervaded by prejudice against racial, ethnic and disabled groups. The online publication of this material for scholarly research purposes is not an endorsement of those views nor a promotion of eugenics in any way.
We developed a simple marker technique called sequence-related amplified polymorphism (SRAP) aimed for the amplification of
open reading frames (ORFs). It is based on two-primer amplification. The primers are 17 or 18 nucleotides long and consist
of the following elements. Core sequences, which are 13 to 14 bases long, where the first 10 or 11 bases starting at the 5′
end, are sequences of no specific constitution (”filler” sequences), followed by the sequence CCGG in the forward primer and
AATT in the reverse primer. The core is followed by three selective nucleotides at the 3′ end. The filler sequences of the
forward and reverse primers must be different from each other and can be 10 or 11 bases long. For the first five cycles the
annealing temperature is set at 35°C. The following 35 cycles are run at 50°C. The amplified DNA fragments are separated by
denaturing acrylamide gels and detected by autoradiography. We tested the marker technique in a series of recombinant inbred
and doubled-haploid lines of Brassica oleracea L. After sequencing, approximately 45% of the gel-isolated bands matched known genes in the Genbank database. Twenty percent
of the SRAP markers were co-dominant, which was demonstrated by sequencing. Construction of a linkage map revealed an even
distribution of the SRAP markers in nine major linkage groups, not differing in this regard to AFLP markers. We successfully
tagged the glucosinolate desaturation gene BoGLS-ALK with these markers. SRAPs were also easily amplified in other crops such as potato, rice, lettuce, Chinese cabbage (Brassica rapa L.), rapeseed (Brassica napus L.), garlic, apple, citrus, and celery. We also amplified cDNA isolated from different tissues of Chinese cabbage, allowing the fingerprinting of these sequences.
A method has been developed which allows the isolation of very high molecular weight DNA (>2 million bp) from leaf protoplasts of tomato (Lycopersicon esculentum). The DNA isolated in this manner was digested in agarose with rare-cutting restriction enzymes and separated by pulsed field gel electrophoresis. The size range of the reslting fragments was determined by hybridization to a number of single copy clones and the suitability of these enzymes for the mapping of large DNA fragments was evaluated. Furthermore, five genetically tightly linked single copy clones have been used to begin the construction of a physical map in a region of the genome containing the Tm-2a gene which confers resistance to tobacco mosaic virus. Two of the five clones were found to be on the same 560 kb SalI fragment and therefore are no further apart than that distance. The remaining three markers are distributed over at least 3 million bp, so that the total minimum physical distance of that cluster is at least 4 million bp. The results are discussed with respect to correlations between recombination frequencies and physical distance as well as physical mapping large regions of a complex plant genome like tomato.
The resistance of sunflower, Helianthus annuus L., to downy mildew, caused by Plasmopara halstedii, is conferred by major genes denoted by Pl. Using degenerate and specific primers, 16 different resistance gene analogs (RGAs) have been cloned and sequenced. Sequence comparison and Southern-blot analysis distinguished six classes of RGA. Two of these classes correspond to TIR-NBS-LRR sequences while the remaining four classes correspond to the non-TIR-NBS-LRR type of resistance genes. The genetic mapping of these RGAs on two segregating F2 populations showed that the non-TIR-NBS-LRR RGAs are clustered and linked to the Pl5/Pl8 locus for resistance to downy mildew in sunflower. These and other results indicate that different Pl loci conferring resistance to the same pathogen races may contain different sequences.
A computerized procedure to construct integrated genetic maps is presented. The computer program (JOINMAP) can handle raw data from F2s, backcrosses and recombinant inbred lines, as well as listed pair-wise recombination frequencies. The procedure is useful for combining linkage data that have been collected in different experiments; the result is a mathematical alignment of the distinct genetic maps. Data from single experiments can be dealt with as well. In view of the fast growing amount of linkage information for molecular markers, which is often being generated by different research groups, integrated maps provide useful information on the map position of genes and DNA markers. The procedure performs a sequential build-up of the map and, at each step, a numerical search for the best fitting order of markers. Weighted least squares is used for the estimation of map distances.
The root knot nematode resistance gene Mi in tomato has been mapped in the pericentromeric region of chromosome 6. With the objective of isolating Mi through a map-based cloning approach, we have previously identified and ordered into a high-resolution genetic linkage map a variety of tightly linked molecular markers. Using pulsed-field gelelectrophoresis and various rarely cutting restriction enzymes in single, double and partial digestions, we now report long-range physical maps of the two closest flanking markers, acid phosphatase-1 (Aps-1) and GP79, which span over 400 and 800 kb, respectively. It is concluded that the physical distance between both markers is larger than predicted on the basis of genetic linkage analysis. Furthermore, two RFLP markers (H3F8 and H4H10) which map genetically to the same locus as Aps-1 do not show physical linkage, indicating severe suppression of recombination in this region of the chromosome. Finally, no evidence was obtained showing the presence of a CpG island near Aps-1.
Plant genes for pathogen resistance can be used to engineer disease resistant crops. Oligonucleotides were designed from sequence motifs conserved between resistance genes of tobacco and Arabidopsis thaliana and used as PCR primers in potato DNA. Amplification products were obtained that were homologous to known resistance genes and linked without recombination with the nematode resistance locus Gro1 and the Phytophthora infestans resistance locus R7 of potato. Map positions of PCR-derived potato gene fragments were also correlated with resistance loci of the related tomato and tobacco genomes. Our results indicate that plant resistance genes that are effective against nematodes, fungi, viruses and bacteria may be isolated based on common sequence motifs and PCR methodology.
Simple sequence repeat (SSR) markers were developed for cultivated sunflower (Helianthus annuus L.) from the DNA sequences of 970 clones isolated from genomic DNA libraries enriched for (CA)n,, (CT)n, (CAA)n, (CATA)n, or (GATA)n. The clones harbored 632 SSRs, of which 259 were unique. SSR markers were developed for 130 unique SSRs by designing and testing primers for 171 unique SSRs. Of the total, 74 SSR markers were polymorphic when screened for length polymorphisms among 16 elite inbred lines. The mean number of alleles per locus was 3.7 for dinucleotide, 3.6 for trinucleotide, and 9.5 for tetranucleotide repeats and the mean polymorphic information content (PIC) scores were 0.53 for dinucleotide, 0.53 for trinucleotide, and 0.83 for tetranucleotide repeats. Cluster analyses uncovered patterns of genetic diversity concordant with patterns produced by RFLP fingerprinting. SSRs were found to be slightly more polymorphic than RFLPs. Several individual SSRs were significantly more polymorphic than RFLP and other DNA markers in sunflower (20% of the polymorphic SSR markers had PIC scores ranging from 0.70 to 0.93). The newly developed SSRs greatly increase the supply of sequence-based DNA markers for DNA fingerprinting, genetic mapping, and molecular breeding in sunflower; however, several hundred additional SSR markers are needed to routinely construct complete genetic maps and saturate the genome.
Metalaxyl resistance in sunflower downy mildew and control through genetics and alternative fungicides
- T J Gulya
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Allelic diversity of simple sequence repeats among elite inbred lines of cultivated sunflower
- J-K J Mangor
- Edwards L Kj Thompson
- Mb Slabaugh
- Knapp
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Molecular markers as a tool in breeding for resistance against sunflower downy mildew
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Molecular markers as a tool in breeding for resistance against sunflower downy mildew
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Colocation of downy mildew (Plasmopara halstedii) resistance genes in sunflower (Helianthus annuus L.)
- P Roeckel-Drevet
- G Gagne
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- L Gentzbittel
- J Philippon
- Tourvieille De Labrouhe
- D Vear
- Roeckel-Drevet