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Inheritance of Resistance to Race 4 of Downy Mildew Derived from Interspecific Crosses in Sunflower
Crop Science
Abstract
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
... Breeding efforts resulted in the identification of new resistance sources providing effective genes like Pl 5 , a major gene giving resistance to pathotype 700, from the open-pollinated Russian cultivars Novinka and Progress, and from the Romanian inbred line RF-S 11 -5566-74 (Vrânceanu et al. 1981;Miller and Gulya 1984;1987). Other resistance genes that became available for the control of P. halstedii (pathotype 730) were Pl 6 , Pl 7 and Pl 8 (Miller and Gulya 1991). The gene Pl 6 was identified in the inbred lines HA-335 and HA-336, both from wild H. annuus, and Pl 7 came from HA-337, HA-338 and HA-339, all of them derived from H. praecox ssp. ...
... It is worth mentioning that some of the genes show a broad-spectrum resistance to P. halstedii and have remained resistant to all races of the pathogen for many years. This is the case of Pl 8 in RHA-340, which controlled all the races of P. halstedii since its release in 1991 (Miller and Gulya 1991) until 2017, when pathogen populations overcoming it were identified in France and Italy (Martin-Sanz et al. 2020). Some other genes are reported to still be able to provide a universal control of the pathogen (i.e. ...
... It might also be possible that they are not all truly different according to their reaction to P. halstedii races. There is the example of Pl 6 -Pl 7 which come from different origins (Miller and Gulya 1991) but are found in the same zone on LG8 (Bouzidi et al. 2002) and which have never been differentiated by their reaction to races: when 304 and similar pathotypes appeared, both showed exactly the same susceptibilities (Tourvieille de Labrouhe et al. 2000). New pathotypes are likely to be able to overcome genes at present giving resistance to all known races of the pathogen, and several of these may be found to be overcome at the same time. ...
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.
... From these wild species inbred lines have been developed, which are then used as donors of resistance genes. Thus, Pl6 was introduced from wild ecotype of H. annuus (Miller and Gulya 1991), Pl5 from H. tuberosus (Vranceanu et al. 1981), Pl7 from H. praecox (Miller and Gulya 1991), and Pl8 and Plarg from H. argophyllus (Miller and Gulya 1991;Seiler et al. 1991). According to Seiler (2012) Along with resistance genes, lines developed from wild sunflower species also inherit a number of undesirable characteristics. ...
... From these wild species inbred lines have been developed, which are then used as donors of resistance genes. Thus, Pl6 was introduced from wild ecotype of H. annuus (Miller and Gulya 1991), Pl5 from H. tuberosus (Vranceanu et al. 1981), Pl7 from H. praecox (Miller and Gulya 1991), and Pl8 and Plarg from H. argophyllus (Miller and Gulya 1991;Seiler et al. 1991). According to Seiler (2012) Along with resistance genes, lines developed from wild sunflower species also inherit a number of undesirable characteristics. ...
... From these wild species inbred lines have been developed, which are then used as donors of resistance genes. Thus, Pl6 was introduced from wild ecotype of H. annuus (Miller and Gulya 1991), Pl5 from H. tuberosus (Vranceanu et al. 1981), Pl7 from H. praecox (Miller and Gulya 1991), and Pl8 and Plarg from H. argophyllus (Miller and Gulya 1991;Seiler et al. 1991). According to Seiler (2012) Along with resistance genes, lines developed from wild sunflower species also inherit a number of undesirable characteristics. ...
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.
... The DM resistance in sunflower and DM virulence in pathogens are consistent with the gene-for-gene hypothesis (Flor 1955), contributing to the use of DM race-specific resistance as the main breeding strategy against downy mildew disease in sunflower. More than twenty Pl genes have currently been reported in cultivated and wild sunflowers, i.e., Pl 1 -Pl 19 , Pl 21 , and Pl Arg (Table S1, Zimmer and Kinman 1972;Miller and Gulya 1991;Mouzeyar et al. 1995;Roeckel-Drevet et al. 1996;Vear et al. 1997Vear et al. , 2008Bert et al. 2001;Rahim et al. 2002;Molinero-Ruiz et al. 2003;Radwan et al. 2003;Vear et al. 2008;Mulpuri et al. 2009;de Romano et al. 2010;Bachlava et al. 2011;Liu et al. 2012;Qi et al. 2015Qi et al. , 2016aZhang et al. 2017). Among these resistance genes, Pl 13 , Pl 14 , Pl 16 , and Pl Arg are localized on linkage group (LG) 1 of the sunflower genome; Pl 1 , Pl 2 , Pl 6 , Pl 7 , and Pl 15 are localized on LG8; Pl 5 , Pl 8 and Pl 21 are localized on LG13; Pl 17 and Pl 19 are localized on LG4; and Pl 18 is localized on LG2. ...
... Pl 5 originated from H. tuberosus L. (Vrânceanu et al. 1981), whereas Pl 7 originated from H. praecox Englem. and Gray (Miller and Gulya 1991), and Pl 8 , Pl Arg , and Pl 18 were derived from H. argophyllus Torrey and Gray (Miller and Gulya 1988;Seiler 1991;Qi et al. 2016a). ...
... Helianthus argophyllus (2n = 2x = 34), a wild diploid annual species, primarily occurs in beach environments or sandy habitats in Texas, U.S. (Rogers et al. 1982;Gulya 2005). This species is an important donor of different disease resistance genes in sunflower, such as rust resistance genes R adv and R 5 (Bachlava et al. 2011;Qi et al. 2012), DM resistance genes Pl 8 , Pl Arg , and Pl 18 (Miller and Gulya 1991;Qi et al. 2016a), and Sclerotinia resistance (Qi et al. 2016b). In an investigation of the DM resistance of H. argophyllus, Gulya (2005) inoculated 13 H. argophyllus accessions with a mixture of P. halstedii races with an aggregate pathogen phenotype of race 777. ...
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.
... Resistance genes Pl1 and Pl2 were first shown to confer resistance to race 100, and races 100 and 300, respectively (Gedil et al. 2001). However, Pl6, Pl7 and Pl8, introduced from wild Helianthus, confer resistance to four races (100, 300, 700 and 730) of P. halstedii (Miller and Gulya 1991). Pl1, Pl2, Pl6 and Pl7 were shown to be grouped into clusters on linkage group 8 of the SSR map (Gedil et al., 2001). ...
... Several lines, sources of Pl6 and Pl7 resistance genes are available. Among them Ha336, a donor of Pl6 gene introduced from wild H. annuus, and Ha338, a donor of Pl7 gene inroduced from H. praecox (Miller and Gulya, 1991). According to the pedigree, and IFLP haplotyping (Slabaugh et al., 2003) of these lines, Pl6 and Pl7, though clustered and conffering resistance to the same races, are different genes. ...
... The first mapping population was formed as described previously (Panković et al., 2007). Shortly, sunflower inbred line Ha26S, with a high general combining ability was used as the recipient of the Pl6 gene from the initial cross with Ha336 (Miller and Gulya 1991). After several cycles of backcrosses Ha26S was converted to a resistant NIL Ha26R. ...
The inheritance of resistance to downy mildew of sunflower was investigated in three mapping populations. From each cross 73 to 75 F 3 families were produced. The resistance of plant material to downy mildew was evaluated by the whole seedling inoculation technique. F 3 families were studied using several PCR and two CAPS markers for resistance gene analogues (RGAs) at Pl6 locus. Seven haplotypes, in coupling or repulsion phase with resistance, five dominant and two co-dominant, were mapped for each mapping population. The results of heterogeneity test between recombination fractions for each marker pair among three families, permitted the construction of composite map. Mapping results are consistent, regardless on the parental lines used as sources of resistance genes. Pozicioniranje CAPS biljega za otpornost na plamenjaču na kartu vezanosti ustanovljenu u tri populacije za kartiranje kod suncokreta Sažetak Nasljeđivanje otpornosti na plamenjaču kod suncokreta je istraživano u tri populacije za kartiranje. Od svakog križanja je proizvedeno 73 do 75 F 3 obitelji. Otpornost biljnog materijala na plamenjaču je procijenjena tehnikom inokulacije cijelih klijanaca. F 3 obitelji su proučavane pomoću nekoliko PCR i dva CAPS biljega za analoge gena za rezistentnost. (RGAs) na Pl6 lokusu. Sedam haplotipova, u seriji spajanja ili razdvajanja s otpornošću, pet dominantnih i dva kodominantna, su kartirana u svakoj populaciji. Rezultati testa heterogenosti između rekombiniranih frakcija za svaki par biljega između tri obitelji, su omogućili konstruiranje sastavljene karte. Rezultati kartiranja su konzistentni, bez obzira na roditeljske linije korištene kao izvor gena za otpornost. Ključne riječi: Helianthus annuus L., Plasmopara halstedii, selekcija pomognuta biljezima (MAS), rascijepljene amplificirane polimorfne sekvence (CAPS) Proceedings. 43 rd Croatian and 3 rd International Symposium on Agriculture. Opatija. Croatia (357-XXX) ORIGINAL SCIENTIFIC PAPER Proceedings. 43 rd Croatian and 3 rd International Symposium on Agriculture. Opatija. Croatia (357-361) ORIGINAL SCIENTIFIC PAPER Dejana SAFTIĆ-PANKOVIĆ, Zlatko ŠATOVIĆ, Nataša RADOVANOVIĆ, Siniša JOCIĆ, Vladimir MIKLIČ 43rd Croatian and 3rd International Symposium on Agriculture
... устойчивость к ложной мучнистой росе [14,15] [15]. Ген Pl arg был картирован в группе сцепления LG1, а Pl 8 в LG13 [9,17]. ...
... устойчивость к ложной мучнистой росе [14,15] [15]. Ген Pl arg был картирован в группе сцепления LG1, а Pl 8 в LG13 [9,17]. ...
Resistance to the downy mildew pathogen Plasmopara halstedii (Farl.) Berlese et de Toni in sunflower is controlled by the resistance gene Pl. The Plarg gene is currently promising in breeding for resistance as it is effective against all known races of the pathogen. This gene is introgressed from the wild species Helianthus argophyllus. Molecular markers and, in particular, simple microsatellite repeats (SSRs) allow to control the transfer and pyramiding of disease resistance genes. However, validation of the molecular marker is needed to prove its reliability. The microsatellite marker ORS 822 was tested to identify the Plarg gene. We conducted the research on a hybrid combination of a susceptible sunflower line of VNIIMK's breeding VK 925 and a resistant line RHA 419, a donor of the Plarg gene. We es-tablished that these lines differ from each other by the allelic state of this locus. Molecular analysis of the F1 generation showed that the microsatellite locus is inherited codominantly. We obtained the F2 generation by self-pollination and made a phytopathological evaluation of resistance to P. halstedii. Split analysis by ph-notype showed that the actually observed segregation corresponded to the theoretically expected 3:1 model for monogenic inheritance of the trait. Based on the obtained data, we determined that the Plarg gene and microsatellite locus ORS 822 are linked with a recombination frequency of 0.26. As a result of this research, we concluded that this marker can be used to select homozygous resistant sunflower plants for resistance to downy mildew in marker-assisted selection (MAS).
... 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.
... Although partly from the same origin, downy mildew resistance from Argentinean populations appears quite specific because, at least in the resources held and lines developed at INRA, they are all resistant to race 710 but susceptible to race 703. According to the ancestry detailed by Romano and Vazquez (2003) Miller and Gulya (1991) developed HA335 and HA336 from crosses with wild H.annuus from Texas with resistance to all known races except those named "xx4", such as 304, 314 and 334, observed in France. Their resistance gene Pl6 was located in the cluster with Pl1 and Pl2. ...
... Resistance from other species : HA337, HA338 and HA339 were all developed from H.praecox by Miller and Gulya (1991), with a gene designated Pl7, but which has not been distinguished from Pl6 by its resistance to different races or its map position. At the same time as the interspecific pool from H.argophyllus was studied, a number of other interspecific pools developed at INRA Montpellier were also tested for their resistance to race 710. ...
New sources of major gene resistance to sunflower downy mildew were compared with known resistance genes. All genes appear to come from crosses with wild Helianthus, and most frequently from wild H.annuus. The gene Pl6 has been found in many different ecotypes but resistances which segregate independently from this gene have also been obtained. Genes considered as different may be the result of intra-cluster recombinations. Only 1 or perhaps 2 genes have been obtained from H.argophyllus. Identification of genes from H.tubersosus, is not complete, possibly because these sources show downy mildew sporulation on cotyledons. Some other annual species also show major gene type resistances. It is concluded that knowledge of these sources is important, both for their use in breeding and also to distinguish between major gene and quantitative resistance.
... The DM R gene cluster was located in the first and largest sub-cluster containing Pl 1 , Pl 2 , Pl 6 , Pl 7 , Pl 15 and Pl 20 and two rust R genes R 1 and R 15 [1]. Pl 20 originated from H. argophyllus is different from other Pl genes in the cluster in which Pl 1 , Pl 2 and Pl 6 were from wild H. annuus, Pl 7 was from H. praecox, and Pl 15 was identified from an Argentinian restorer inbred line [1,[27][28][29][30][31]. Pl 20 was immune to all P. halstedii races identified in North America, including those predominant and virulent races; however, the remaining Pl genes, except Pl 15 in the cluster, have already been overcome by some or all of the identified P. halstedii races. ...
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.
... The four isolates resulted in clear resistant (0% DM incidence) or susceptible (100% DM incidence) reactions of the differentials. They were identified as race 705, since they caused disease on HA304 (universal susceptible), RHA265 (Pl 1 ), and RHA274 (Pl 2 ) lines, as well as on HAR4 (Pl 16 ) and HA335 (Pl 6 ) (Miller and Gulya, 1991) lines (García-Carneros and Molinero-Ruiz, 2017). ...
The control of soilborne crop pathogens is conditioned by the limited management options due to difficult access to active infection courts and to restrictions in the use of synthetic pesticides in Europe. For most soilborne sunflower pathogens, an effective management relies on genetic resistance which is, however, hindered by new pathogen populations (new races). Special emphasis is thus put on updated monitoring and characterization of pathogens and on the enlargement of the set of tools for disease management. Concerning characterization, advances on the population structure of Verticillium dahliae affecting sunflower by means of genetic, molecular and pathogenic approaches are presented. Also in relation to increases of sunflower wilt diseases recently observed, the fungus Cadophora malorum has been identified in Russia and reported as a new pathogen of this crop. Third, new races of Plasmopara halstedii (sunflower downy mildew), have been identified in Spain and Portugal. Most of them have a high virulence, since they overcome several genes for resistance. With regard to alternatives for disease control, entomopathogenic fungi (EF) constitute a novel tool. Used for years in Integrated Pest Management strategies due to their efficacy in controlling insect pests affecting crops, new ecological roles of these fungi have recently been reported. The EF species Beauveria bassiana and Metarhizium brunneum have been assessed by their in vitro effect against V. dahliae and C. malorum by our research group. Our results suggest that antibiosis and/or competition for ecological niche are operating in some EF-pathogen interactions. In summary, pathogen characterization is essential for genetic resistance for worldwide environments of sunflower production. Moreover, the security of sunflower yield and profitability is dependent not only on effective genetic resistance, but also on additional new control options that can be included in successful strategies of sunflower disease management.
... line 953-102-1-1, which is a selection involving wild H. annuus (Fick and Zimmer, 1974;Vear et al., 2008). The Pl 5 originated from H. tuberosus (Vranceanu et al., 1981), Pl 6 was derived from wild non-cultivated H. annuus and Pl 7 from H. praecox Englem and Gray (Miller and Gulya, 1991). Two Pl genes, Pl 8 and Pl Arg, were also derived from H. argophyllus Torrey and Gray (Seiler, 1991). ...
Downy mildew caused by Plasmopara halstedii is one of the most economically important fungal diseases on sunflower (Helianthus annuus). To date, several downy mildew resistance genes called Pl genes have been reported on sunflower genetic map. Previous findings have confirmed that Iranian sunflower germplasms are harbouring Pl resistance genes that may be used to control downy mildew. In the current study, there were investigated the Pl5 and Pl16 downy mildew resistance genes in 51 inbred lines of Iranian sunflower, using PCR-based method. Fifteen differential lines carrying Pl5 and Pl16 downy mildew resistance genes were used as positive control. DNAs from 51 sunflower inbred lines were used in PCR reactions using primer pair RS1008 and Hap3 previously reported to serve as tightly linked to Pl16 and P5 loci, respectively. The PCR results confirmed the presence of two Pl16 and Pl5 bands with the size of about 280 and 1,580 bp, respectively, in differential lines. The results indicated that 1 inbred line out of 51 was found to carry Pl5 gene and 10 lines were found to carry Pl16 gene across the studied Iranian sunflower genotypes. These findings may be used to assist breeders for conservation and selection of downy mildew resistant sunflower genotypes.
... When first released , they were initially selected only for resistance to Races 1, 2, and 3, but have been immune to all subsequent races. When these interspecific crosses were studied for resistance to Race 4, three different genes were identified: Pl6 from the wild H. annuus crosses, Pl7 from the H. praecox parent, and Pl8 from H. argophyllus (Miller and Gulya, 1991). The inheritance of resistance of these lines to other races has not been studied, thus it is not known whether a single gene confers non-race-specific immunity, or a cluster of tightly linked genes is responsible. ...
... Pl5, Pl6 and Pl7 are three Pl loci conferring resistance to pathotype 710, for which near-isogenic introgressed lines are available. Pl5 originated from H. tuberosus (a perennial species) (Vranceanu et al., 1981), Pl6 was derived from wild non-cultivated H. annuus and Pl7 from H. praecox Englem and Gray (Miller and Gulya, 1991). Pl6 and Pl7 are localized in a large genomic region of LG 8 called cluster Pl6/Pl7, close to, but genetically different from the cluster Pl1/Pl2, which does not confer resistance to pathotype 710 (Vear et al., 1997). ...
Plasmopara halstedii is an obligate biotrophic oomycete causing downy mildew disease on sunflower, Helianthus annuus, an economically important oil crop. Severe symptoms of the disease (e.g., plant dwarfism, leaf bleaching, sporulation and production of infertile flower) strongly impair seed yield. Pl resistance genes conferring resistance to specific P. halstedii pathotypes were located on sunflower genetic map but yet not cloned. They are present in cultivated lines to protect them against downy mildew disease. Among the 16 different P. halstedii pathotypes recorded in France, pathotype 710 is frequently found, and therefore continuously controlled in sunflower by different Pl genes. High-throughput sequencing of cDNA from P. halstedii led us to identify potential effectors with the characteristic RXLR or CRN motifs described in other oomycetes. Expression of six P. halstedii putative effectors, five RXLR and one CRN, was analyzed by qRT-PCR in pathogen spores and in the pathogen infecting sunflower leaves and selected for functional analyses. We developed a new method for transient expression in sunflower plant leaves and showed for the first time subcellular localization of P. halstedii effectors fused to a fluorescent protein in sunflower leaf cells. Overexpression of the CRN and of 3 RXLR effectors induced hypersensitive-like cell death reactions in some sunflower near-isogenic lines resistant to pathotype 710 and not in susceptible corresponding lines, suggesting they could be involved in Pl loci-mediated resistances.
... Pl5, Pl6 and Pl7 are three Pl loci conferring resistance to pathotype 710, for which near-isogenic introgressed lines are available. Pl5 originated from H. tuberosus (a perennial species) (Vranceanu et al., 1981), Pl6 was derived from wild non-cultivated H. annuus and Pl7 from H. praecox Englem and Gray (Miller and Gulya, 1991). Pl6 and Pl7 are localized in a large genomic region of LG 8 called cluster Pl6/Pl7, close to, but genetically different from the cluster Pl1/Pl2, which does not confer resistance to pathotype 710 (Vear et al., 1997). ...
Plasmopara halstedii is an obligate biotrophic oomycete causing downy mildew disease on sunflower, Helianthus annuus, an economically important oil crop. Severe symptoms of the disease (e.g., plant dwarfism, leaf bleaching, sporulation and production of infertile flower) strongly impair seed yield. Pl resistance genes conferring resistance to specific P. halstedii pathotypes were located on sunflower genetic map but yet not cloned. They are present in cultivated lines to protect them against downy mildew disease. Among the 16 different P. halstedii pathotypes recorded in France, pathotype 710 is frequently found, and therefore continuously controlled in sunflower by different Pl genes. High-throughput sequencing of cDNA from P. halstedii led us to identify potential effectors with the characteristic RXLR or CRN motifs described in other oomycetes. Expression of six P. halstedii putative effectors, five RXLR and one CRN, was analyzed by qRT-PCR in pathogen spores and in the pathogen infecting sunflower leaves and selected for functional analyses. We developed a new method for transient expression in sunflower plant leaves and showed for the first time subcellular localization of P. halstedii effectors fused to a fluorescent protein in sunflower leaf cells. Overexpression of the CRN and of 3 RXLR effectors induced hypersensitive-like cell death reactions in some sunflower near-isogenic lines resistant to pathotype 710 and not in susceptible corresponding lines, suggesting they could be involved in Pl loci-mediated resistances.
... Sunflower wild species of H. annuus are an important source of downy mildew resistance and other disease resistances (for review see Seiler and Jan 2010). Among 15 mapped downy mildew Pl genes (Pl 1 , Pl 2 , Pl 5 -Pl 8 , Pl 13 -Pl 19 , Pl 21 , and Pl Arg ), six (Pl 1 , Pl 2 , Pl 6 , Pl 13 , Pl 17 , and Pl 19 ) are known to originate from the wild H. annuus (Fick and Zimmer 1974;Miller and Gulya 1991;Vear et al. 2008). These Pl genes from H. annuus tend to appear as a gene cluster in the sunflower genome. ...
Key message:
A new downy mildew resistance gene, Pl 19 , was identified from wild Helianthus annuus accession PI 435414, introduced to confection sunflower, and genetically mapped to linkage group 4 of the sunflower genome. Wild Helianthus annuus accession PI 435414 exhibited resistance to downy mildew, which is one of the most destructive diseases to sunflower production globally. Evaluation of the 140 BC1F2:3 families derived from the cross of CMS CONFSCLB1 and PI 435414 against Plasmopara halstedii race 734 revealed that a single dominant gene controls downy mildew resistance in the population. Bulked segregant analysis conducted in the BC1F2 population with 860 simple sequence repeat (SSR) markers indicated that the resistance derived from wild H. annuus was associated with SSR markers located on linkage group (LG) 4 of the sunflower genome. To map and tag this resistance locus, designated Pl 19 , 140 BC1F2 individuals were used to construct a linkage map of the gene region. Two SSR markers, ORS963 and HT298, were linked to Pl 19 within a distance of 4.7 cM. After screening 27 additional single nucleotide polymorphism (SNP) markers previously mapped to this region, two flanking SNP markers, NSA_003564 and NSA_006089, were identified as surrounding the Pl 19 gene at a distance of 0.6 cM from each side. Genetic analysis indicated that Pl 19 is different from Pl 17 , which had previously been mapped to LG4, but is closely linked to Pl 17 . This new gene is highly effective against the most predominant and virulent races of P. halstedii currently identified in North America and is the first downy mildew resistance gene that has been transferred to confection sunflower. The selected resistant germplasm derived from homozygous BC2F3 progeny provides a novel gene for use in confection sunflower breeding programs.
... When first released , they were initially selected only for resistance to Races 1, 2, and 3, but have been immune to all subsequent races. When these interspecific crosses were studied for resistance to Race 4, three different genes were identified: Pl6 from the wild H. annuus crosses, Pl7 from the H. praecox parent, and Pl8 from H. argophyllus (Miller and Gulya, 1991). The inheritance of resistance of these lines to other races has not been studied, thus it is not known whether a single gene confers non-race-specific immunity, or a cluster of tightly linked genes is responsible. ...
Sunflower is a known host for over 30 pathogens, but the relative importance of specific diseases varies with geographic region. Differences in climate, pathogen distribution, and cropping practices affect the prevalence of individual diseases in each region. This chapter discusses two tables of selected diseases, which list diseases considered to be of widespread importance, and selected diseases of regional importance or those that may occur sporadically. It also discusses individual diseases like Downy mildew, Phomopsis stem canker, rust, Rhizopus head rot, Sclerotinia head rot, Sclerotinia stalk rot and wilt, and Verticillium wilt, and their effects on sunflower production. Sunflower producers face several challenges when managing sunflower diseases, most notably pathogens that can cause significant yield loss under a variety of environmental conditions, variable pathogens, and limited management tools to the most devastating diseases. However, pathologists and breeders are continually working to develop and deploy new management tools that can mitigate yield losses to diseases.
... When first released , they were initially selected only for resistance to Races 1, 2, and 3, but have been immune to all subsequent races. When these interspecific crosses were studied for resistance to Race 4, three different genes were identified: Pl6 from the wild H. annuus crosses, Pl7 from the H. praecox parent, and Pl8 from H. argophyllus (Miller & Gulya, 1991). The inheritance of resistance of these lines to other races has not been studied, thus it is not known whether a single gene confers nonrace-specific immunity, or a cluster of tightly linked genes is responsible. ...
... In France, five races (100, 300, 700, 703, 710) have been identified (Tourvieille,1999). The resistance genes at present denoted Pl5 (from Progress (Helianthus tuberosus ?), INRA line XRQ), Pl6 (from wild H.annuus, USDA line HA335) , Pl7 (from H.praecox, USDA line HA338), Pl8 (from H.argophyllus, USDA line RHA340) (Miller and Gulya, 1991) and a further source of resistance provided by R. Urs (personal communication, 1984 , INRA line YSQ) give resistance to all these races. The INRA line PMI3, bred from DM2 (Novinka) gives resistance to all French races except 710, whereas the INRA line QHP1, bred from HAR5 (Charata.INTA), is resistant to all except 703. ...
... Pl genes are located on complex loci containing several genes tightly linked. Because of the complexity of the loci, no Pl gene has been cloned yet (Miller & Gulya 1991). The Pl genes have been localized on four clusters in sunflower. ...
In order to clarify the role of Pl2 resistance gene in differentiation the pathogenicity in Plasmopara halstedii (sunflower downy mildew), analyses were carried out in four pathotypes: isolates of races 304 and 314 that do not overcome Pl2 gene, and isolates of races 704 and 714 that can overcome Pl2 gene. Based on the reaction for the P. halstedii isolates to sunflower hybrids varying only in Pl resistance genes, isolates of races 704 and 714 were more virulent than isolates of races 304 and 314. Index of aggressiveness was calculated for pathogen isolates and revealed the presence of significant differences between isolates of races 304 and 314 (more aggressive) and isolates of races 704 and 714 (less aggressive). There were morphological and genetic variations for the four P. halstedii isolates without a correlation with pathogenic diversity. The importance of the Pl2 resistance gene to differentiate the pathogenicity in sunflower downy mildew was discussed.
... Currently, 18 downy mildew resistance genes (Pl 1 -Pl 16 , Pl 21 , and Pl ARG ) have been reported in cultivated and wild species of sunflowers (Zimmer and Kinman 1972;Miller and Gulya 1991;Mouzeyar et al. 1995;Roeckel-Drevet et al. 1996;Vear et al. 1997Vear et al. , 2008Rahim et al. 2002;Molinero-Ruiz et al. 2003;Vear et al. 2008;Mulpuri et al. 2009;de Romano et al. 2010;Bachlava et al. 2011;Liu et al. 2012). However, many of these genes no longer condition resistance to most races, because virulent downy mildew races have increased in prevalence in response to the release of sunflower hybrids with race-specific resistance genes Molinero-Ruiz et al. 2000;Rashid et al. 2006;Gulya 2007;Gulya et al. 2011). ...
Key message:
Pl 17, a novel downy mildew resistance gene independent of known downy mildew resistance genes in sunflowers, was genetically mapped to linkage group 4 of the sunflower genome. Downy mildew (DM), caused by Plasmopara halstedii (Farl.). Berl. et de Toni, is one of the serious sunflower diseases in the world due to its high virulence and the variability of the pathogen. DM resistance in the USDA inbred line, HA 458, has been shown to be effective against all virulent races of P. halstedii currently identified in the USA. To determine the chromosomal location of this resistance, 186 F 2:3 families derived from a cross of HA 458 with HA 234 were phenotyped for their resistance to race 734 of P. halstedii. The segregation ratio of the population supported that the resistance was controlled by a single dominant gene, Pl 17. Simple sequence repeat (SSR) and single nucleotide polymorphism (SNP) primers were used to identify molecular markers linked to Pl 17. Bulked segregant analysis using 849 SSR markers located Pl 17 to linkage group (LG) 4, which is the first DM gene discovered in this linkage group. An F2 population of 186 individuals was screened with polymorphic SSR and SNP primers from LG4. Two flanking markers, SNP SFW04052 and SSR ORS963, delineated Pl 17 in an interval of 3.0 cM. The markers linked to Pl 17 were validated in a BC3 population. A search for the physical location of flanking markers in sunflower genome sequences revealed that the Pl 17 region had a recombination frequency of 0.59 Mb/cM, which was a fourfold higher recombination rate relative to the genomic average. This region can be considered amenable to molecular manipulation for further map-based cloning of Pl 17.
... Genetic analysis of downy mildew resistance includes the characterization and inheritance of both complete and partial resistance (Jocic et al., 2012). Complete, monogenic or qualitative resistance is given by Pl genes (Vranceanu et al., 1981;Miller and Gulya 1991). Until today, a total of 18 disease resistance genes have been identified from wild and cultivated sunflower (Pl 1 to Pl 16 , P 21 , Pl Arg ). ...
Since sunflower domestication by pre-hispanic American cultures at least 3000 BC, the use of empiric and scientifically based genetics led to an amazing genetic diversification of the crop going from sophisticated nutraceutical applications up to ornamental purposes, including the traditional confectionary and oilseed production. Commercial sunflower breeding based on genetics started in the first half of the twentieth century and genomics at its endings, with breeding efforts being directed towards the most economically important traits such as increasing seed and oil yield, improving quality traits and conferring resistance or tolerance to biotic and abiotic stresses. In the last few years, advancements in genotyping and sequencing technologies allowed the development of increasingly dense genetic and physical maps, enabling the development of new breeding strategies based on molecular markers, like QTL mapping, association mapping and genomic selection. The need to increase efficiency and precision has motivated the application of marker assisted selection (MAS) in sunflower breeding programs. This chapter will review the different genomic breeding approaches that are currently used to improve sunflower tolerance to biotic and abiotic stresses, increase oil quality and enhance agronomic yield associated traits in order to reduce the gap between potential and actual sunflower production in the present cultivated sunflower area and under global weather changing conditions that negatively impact on it. An overview of the state of the art on sunflower genomics is presented and the potential of high throughput sequencing and genotyping technologies for crop breeding is discussed.
... As new races can be only partially controlled by fungicides, genetic resistance to specific races of P. halstedii is one of the approaches in breeding for resistance to downy mildew (Škorić, 1992;Jan et al., 2004). Among the twelve genes that confer the resistance to P. halstedii (Rahim et al., 2002), Pl6, introduced from wild Helianthus, confers the resistance to four most abundant races (Miller and Gulya, 1991). Sunflower inbred line Ha26 S, with high general combining ability (Škorić et al., 2000), was used as a recipient of the Pl6 gene, and after several cycles of backcrosses was converted to a resistant NIL Ha-26R (Panković et al., 2004Saftić-Panković et al., 2005). ...
RÉSUMÉ
Deux lignées quasi-isogéniques de tournesol, l’une résistante (gène +Pl6) et l’autre sensible (gène -Pl6) au mildiou ont été examinées dans cet article. Les jeunes plantes au stade de la première paire de feuilles ont été soumises à une infection secondaire avec une suspension de spores Plasmopara halstedii. Dans les échantillons recueillis 12 heures aprs l’infection, le contenu de composés phénoliques dans les extraits méthanoliques des feuilles congelées a été analysé par la méthode HPLC. L’activité POD a été déterminée spectrophotométriquement et les isoformes par isoélectrophorèse.
Le contenu constitutif des composés phénoliques et leur accumulation après l’infection étaient plus élevés dans la lignée sensible que dans la lignée résistante. La plus grande quantité POD dans les feuilles NS-H-26R était en corrélation avec une activité augmentée de POD dpendant de gaïacol et avec de faibles totaux de contenus phénoliques. Après l’infection, l’activité POD dépendante de gaïacol et d’acide chlorogénique a augmenté de manière significative dans les deux lignées. L’activité POD dépendante-scopolétine a été induite après infection seulement dans NS-H-26R. L’électrophorèse IEF a révélé l’existence de quatre isoformes anioniques de peroxydase dans les feuilles des deux lignées. L’isoforme principale (pI 5) est particulièrement intensifiée dans la lignée résistante.
L’activité dépendante scopolétine qui est induite après infection seulement dans les lignées NIL résistantes indiquent un rôle spécifique du POD dans le métabolisme de la coumarine qui est probablement lié à la présence du gène Pl6.
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).
From domestication to the present time, agricultural crops have been constantly threatened by pathogens and pests that cause harvest losses, often leading to famine and social unrest. Global climate change, enhanced volume of trade and increased human mobility over the past 50 years are key risk factors in the introduction and establishment of non-native species in new areas. These invaders are a major threat worldwide due to their effect on human health, global food security and livelihoods, disruption of trade, biodiversity, habitat destruction, loss of agricultural productivity and high disease risk to crop plants. The given work have made an attempt to summarize the current knowledge with reference to the spread, frequency, genetics, evolution, diversity of pathogens, especially in sunflower, with some forecasts of the development of different diseases and recommendations for combating them in the context of climate change at the global level.
Sunflower (Helianthus L.) production ranked third in global oilseed production in 2021. Downy mildew (DM), caused by the oomycete pathogen Plasmopara halstedii (Farl.) Berl. et de Toni, is a major constraint for worldwide sunflower production, causing significant yield losses in susceptible hybrids. The search for new sources of resistance to DM is the primary objective of all sunflower breeding programs. Germplasms HA‐DM15 (Reg. no. GP‐385, PI 702359) and HA‐DM16 (Reg. no. GP‐386, PI 702360) were developed by introgressing two new DM resistance genes, Pl37 and Pl38, from the wild sunflower species H. annuus and H. praecox into oilseed sunflower, respectively. The BC1F3‐derived HA‐DM15 harboring the Pl37 gene was selected from the cross of HA 89//NMS HA 89/wild H. annuus PI 435417. The germplasm line HA‐DM16 carrying the Pl38 gene is an improved oilseed derivative of Rf PRA‐417 with DM resistance originally derived from the wild H. praecox PRA‐417 from the cross of cytoplasmic male sterile (CMS) HA89*2/wild H. praecox PRA‐417. HA‐DM15/Pl37 and HA‐DM16/Pl38 are immue to the most predominant and virulent DM races idenfied in North America and Europe. Pl37 and Pl38 have been genetically mapped to sunflower chromosomes 4 and 2, respectively, with single nucleotide polymorphism markers linked to the both genes facilitating their transfer to elite sunflower lines by marker‐assisted selection, providing new and diverse sources for sunflower DM‐resistance breeding.
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.
The sunflower inbred line 33G was used as the experimental material, which was planted in the downy mildew disease nursery and the normal field, respectively, to examine changes in metabolites differences in metabolic pathways, and the mechanism of regulation of metabolic pathways in the process of sunflower susceptible to downy mildew. At the seedling stage, six biological replicates were collected from the leaves of diseased plants in the disease nursery and non-diseased plants in the normal field, respectively (S33G in the disease nursery and R33G in the normal field). The alterations in metabolites and metabolic pathways in susceptible and normal plants were studied by using LC/MS technology. The results demonstrate that in the S33G-R33G comparison group, 679 differentially expressed metabolites are screened, with 294 up-regulated metabolites and 385 down-regulated metabolites, and the differential metabolites are enriched to 58 metabolic pathways. Alkaloids, fatty acids, flavonoids, terpenoids, and polyketones are the most up-regulated differential metabolites, while lipids and lipid molecules, organic oxygen compounds, organic acids and derivatives, and other compounds are the most down-regulated differential metabolites. By comparison, it is discovered that arachidonic acid metabolism, diterpene biosynthesis, purine metabolism, oxidative phosphorylation, α-linolenic acid metabolism, citrate cycle (TCA cycle), nicotinate and nicotinamide metabolic pathways are considerably activated.
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.
Diaporthe gulyae and D. helianthi cause Phomopsis stem canker of sunflower (Helianthus annuus L.) in the United States. Since Phomopsis stem canker did not gain importance until the disease epidemic in 2010, limited studies were conducted to understand the genetic basis of sunflower resistance to D. gulyae and D. helianthi. The objectives of this study were to evaluate the USDA cultivated accessions for resistance to D. gulyae and D. helianthi as well as to utilize genome-wide association studies (GWAS) to identify quantitative trait loci (QTLs) and putative candidate genes underlying those loci common to both organisms. For each fungus, 213 accessions were screened in a complete randomized design in the greenhouse and the experiment was repeated once. Six plants per accession were inoculated with a single isolate of D. gulyae or D. helianthi at four to six true leaves using the mycelium-contact inoculation method. At 15 days (D. gulyae) and 30 days (D. helianthi) post-inoculation, accessions were evaluated for disease severity and compared with the susceptible confection inbred, PI 552934. GWAS identified 28 QTLs common to the two fungi and 24 genes overlapped close to these QTLs. Additionally, it was observed that the resistance QTLs derived mainly from landraces rather than from wild species. Seventeen putative candidate genes associated with resistance to D. gulyae and/or D. helianthi were identified that maybe related to plant-pathogen interactions. These findings advanced our understanding on the genetic basis of resistance to D. gulyae and D. helianthi and will help develop resources for genomics-assisted breeding.
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.
Globally, sunflower (Helianthus annuus L.) occupies a prominent position among edible oilseed crops, and its credit goes to the systematic breeding efforts performed in this crop, especially for oil content during the first half and exploitation of heterosis in the middle of the second half of the twentieth century. Today, sunflower ranks second biggest crop after maize cultivated through hybrid seed worldwide. Primarily, major breeding objectives in sunflower focused in seed and oil yield. However, with changing market demands, current breeding objectives in sunflower have shifted to oil quality along with productivity constraints prevalent in specific agro-climatic zone. The narrow genetic base of cultivated sunflower led main thrust for extensive utilization of both wild genetic resources and mutagenesis through conventional breeding for a long time now. This resulted in the creation of substantial genetic variability for different traits of interest, but progress in this field has been relatively slow and limited. The rapid advances in marker technology paved the way for molecular breeding in sunflower as a tool for acceleration of the breeding process. From the last three decades, a large number of random as well as gene-specific molecular markers have been developed and validated in sunflower, but their application depends on the research objectives. Moreover, recent large-scale DNA sequencing and high-throughput screening techniques transformed the way that crop breeding is performed. In present day, reverse genetics approaches have also become an important goal for researcher in many crops including sunflower. New molecular methodologies such as TILLING including EcoTILLING which entails detection of natural variation allowed to utilize induced as well as existing genetic variation for development of new varieties. In this chapter, we summarized information on available genetic resources, genetics of different traits together with validated molecular markers for their utilization in sunflower breeding programme. Finally, this chapter also reviewed the application of product-based alternative new breeding techniques, as the products developed in this manner could occur naturally over time.
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.
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.
Plant biotrophic oomycetes cause significant production problems and economic losses in modern agriculture and are controlled by fungicide applications and resistance breeding. However, high genetic variability and fast adaptation of the pathogens counteract these measures. As a consequence of the “arms race,” new pathogen phenotypes recurrently occur and may rapidly dominate the population when selected through the pressure of control measures. Intensive monitoring with fast and reliable identification of virulence phenotypes is essential to avoid epidemics and the economic consequences in agriculture. For some of the most important downy mildews and white blister rusts, bioassay-based differentiation has been established to classify infectivity of field isolates or cultivated strains on hosts of defined resistance. However, the testing is laborious, time-consuming, logistically demanding, and prone to impreciseness. Alternatively, host independent classification could overcome these problems and enable fast assessment of the infection risk when monitoring the local pathogen population. The prerequisite would be the identification of pathogen characters correlating with the infection behavior. This review examines the current situation of bioassay-based pathotyping in six of the most important biotrophic oomycetes (Plasmopara viticola, Plasmopara halstedii, Pseudoperonospora cubensis, Peronospora tabacina, Bremia lactucae, and Albugo candida) and gives an overview on attempts and progress to identify genetic markers of the pathogens that correlate with their infection behavior.
Sclerotinia basal stalk rot (BSR) and downy mildew (DM) are two fungal diseases that are major yield limiting factors in global sunflower (Helianthus annuus L.) production. Four oilseed sunflower germplasm lines, HA-BSR2 (Reg. No. GP-346, PI 685015), HA-BSR3 (Reg. No. GP-347, PI 685016), HA-BSR4 (Reg. No. GP-348, PI 685017), and HA-BSR5 (Reg. No. GP-349, PI 685018), were developed to provide diversity for resistance to BSR and DM. The BSR resistance in HA-BSR2 was derived from the wild annual H. petiolaris PI 435843, while BSR resistance in HA-BSR3 to HA-BSR5 was derived from wild annual H. argophyllus PI 494573. The four lines were tested for resistance to BSR in inoculated field nurseries from 2012 to 2015 and consistently showed high levels of BSR resistance across environments. A 4-yr mean BSR disease incidence for HA-BSR2, HA-BSR3, HA-BSR4 and HA-BSR5 was 4.4, 3.0, 0.8, and 1.9%, respectively, compared with an average disease incidence of 36.1% for ‘Cargill 270’ (susceptible hybrid check), 31.0% for HA 89 (recurrent parent), 19.5% for HA 441 (resistant check), and 11.6% for ‘Croplan 305’ (resistant hybrid check). Genetic analysis detected the presence of wild sunflower species chromosome segments in all four germplasm lines, which are presumably associated with BSR resistance. HA-BSR2, HA-BSR3, and HA-BSR4 are also resistant to DM, derived from the parental line HA 458. HA-BSR2, HA-BSR3, and HA-BSR4 represent the first sunflower germplasm to combine resistance against both Sclerotinia BSR and DM.
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.
Sunflower (Helianthus annuus L.) plants with symptoms of stunting and chlorotic leaves were observed in the summer of 2016 in two fields of sunflower under pivot irrigation in Fuentes de Andalucia (Spain) and Serpa (Portugal). The fields showed incidences as much as 50% and symptoms affected two commercial hybrids carrying both resistance genes Pl2 and Pl6. Symptoms of chlorosis entirely covered young leaves. In the lowest leaves of the plants chlorosis was limited to the area bordering the main veins. Chlorotic areas matched with structures of the pathogen observed on the underside of the leaves, particularly in young lesions. Two isolates were recovered from each location and the morphology of structures, sporangiophores and sporangia allowed the identification of Plasmopara halstedii Farl. Berl. & de Toni (Hall 1989). The identification of P. halstedii was confirmed by amplification of the nuclear DNA coding for the large ribosomal unit (28S rDNA) with LR0R and LR6-O primers (Riethmuller et al. 2002). ...
Conservation of crop wild relatives (CWR) has always been predicated on the promise of new and useful traits, and thus modern genetics and genomics tools must help fulfill the promise and continue to secure the conservation of these resources. However, the vast genetic potential present in CWR is often difficult to tap, as identification of superior alleles can be hampered by the effects of the environment on expression of these alleles, and masked in different genetic backgrounds; and transfer of superior alleles into breeding pools to create new crop varieties can be slow and expensive. Some crop species have been more amenable to introgression of traits from wild relatives than others. In some cases, these species may be less diverged fromtheir wild ancestors, which become a good source of mono- to oligogenic traits, many of which are more qualitative in nature, and sometimes of quantitative traits. Sunflower (Helianthus annuus L.) is an introgression success story, and many traits, including cytoplasmic male sterility, herbicide tolerance, drought and biotic stress resistance, and modified fatty acid profiles, have been introgressed into the cultivated gene pool from wild relatives without depression of oil yield and quality. Others, including maize (Zea mays L.), have shown little progress in widening the cultivated gene pool using exotic sources due to temporary yield depression, potential for loss of quality, and disturbance of current logistical habits. Here, we review the breeding history of sunflower and maize, and explore variables that have limited the use of CWR in some species and allowed success in others. Surprisingly, in both sunflower and maize, biological limitations are similar and smaller than expected, and appear to be surmountable with sufficient determination. Possible new technologies and policies to allow a deeper mining of these genetic resources in all crop species are discussed.
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.
Acetohydroxyacid synthase (AHAS) inhibiting herbicides have played a significant role in effective weed control in the cultivation of sunflower since their discovery. The development of sunflower lines and hybrids resistant to these herbicides made their post-emergence application possible. In this study, wild
Helianthus
species were screened phenotypically for imidazolinone (IMI) and sulfonylurea (SU) resistance by herbicide spray and for allelic variations at
Ahasl1
(Ahas1 large subunit) locus using simple sequence repeat and single nucleotide polymorphism markers.
Helianthus praecox
accession 1823 plants showed promising resistance to three classes of SU-based herbicides and
Helianthus nuttallii
accession NUT05 plants remained green for a longer time after imazethapyr spray. A total of 50 accessions belonging to 21 wild
Helianthus
species of different ploidy levels were analysed for allelic variation along with some parents of commercial sunflower hybrids. None of the wild species showed the resistant allele (
Ahasl1-1
) similar to SCG101 (IMI-resistant line), although it is present in some of the parental lines of hybrids. However, the parental lines having
Ahasl1-1
-type allele failed to survive the field dose of imazethapyr spray. Inter-species and inter-accessional allelic variation could be observed among the species. PRA1823 and NUT05 showed repeat length variations at
Ahasl1
locus. Sequencing of full length
Ahasl1
gene from both these accessions did not reveal any resistance mutations in the protein sequences. The molecular basis of the phenotypes identified in this study could be explored further and utilized in breeding programmes for imparting herbicide resistance in cultivated hybrids across sunflower growing regions of the world.
Downy mildew caused by Plasmopara halstedii is one of the major dangers of sunflower in most of the world’s growing areas. A number of major dominant resistance genes (Pl genes) have been either identified in cultivated sunflower or were introduced from wild Helianthus annuus or other wild Helianthus species. However, many aspects of the resistance genetics remain unclear. RAPD and AFLP analysis of near isogenic lines differing in the Pl
2 locus and bulked segregant analysis (BSA) of F2 populations, segregating for race 7 and 9 resistances originating from H. annuus (Pl
2), and race 5 resistance derived from H. annuus (Pl
6) and H. argophyllus (Pl
arg) respectively, were used to identify molecular markers for different sources of resistance against downy mildew. On the basis of these markers, linkage maps for both populations were constructed representing the genomic regions carrying the respective resistance locus. The investigations confirmed the close relationship of Pl2 and Pl6, whereas no association was found for loci Pl2 and Plarg.
Key message:
A novel downy mildew resistance gene, Pl 18 , was introgressed from wild Helianthus argophyllus into cultivated sunflower and genetically mapped to linkage group 2 of the sunflower genome. The new germplasm, HA-DM1, carrying Pl 18 has been released to the public. Sunflower downy mildew (DM) is considered to be the most destructive foliar disease that has spread to every major sunflower-growing country of the world, except Australia. A new dominant downy mildew resistance gene (Pl 18 ) transferred from wild Helianthus argophyllus (PI 494573) into cultivated sunflower was mapped to linkage group (LG) 2 of the sunflower genome using bulked segregant analysis with 869 simple sequence repeat (SSR) markers. Phenotyping 142 BC1F2:3 families derived from the cross of HA 89 and H. argophyllus confirmed the single gene inheritance of resistance. Since no other Pl gene has been mapped to LG2, this gene was novel and designated as Pl 18. SSR markers CRT214 and ORS203 flanked Pl 18 at a genetic distance of 1.1 and 0.4 cM, respectively. Forty-six single nucleotide polymorphism (SNP) markers that cover the Pl 18 region were surveyed for saturation mapping of the region. Six co-segregating SNP markers were 1.2 cM distal to Pl 18 , and another four co-segregating SNP markers were 0.9 cM proximal to Pl 18 . The new BC2F4-derived germplasm, HA-DM1, carrying Pl 18 has been released to the public. This new line is highly resistant to all Plasmopara halstedii races identified in the USA providing breeders with an effective new source of resistance against downy mildew in sunflower. The molecular markers that were developed will be especially useful in marker-assisted selection and pyramiding of Pl resistance genes because of their close proximity to the gene and the availability of high-throughput SNP detection assays.
The presence of milk thistle fruits biologically active substances in the irradiated rats males organism essentially effects on the functional activity in their posterity small intestine. Usage of milk thistle fruits by the rats females due to the lactation optimizes the results of the irradiation of the rats males in the small intestine of their posterity was shown. The normalizing effect of the milk thistle fruits realizes with the gender differences: the data of the functional activity were the highest in the group of the irradiated hungry males rats and intact females, which got the milk thistle fruits due to the lactation
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