No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Registration of Six Downy Mildew Resistant Sunflower Germplasm Lines
Crop Science
... Downy mildew can be controlled by single, race-specific dominant resistance genes. Multi-race resistant germplasm and single-race resistant germplasms have been developed from crosses with wild sunflower (Miller and Gulya, 1988;Tan et al., 1992;Jan et al., 2004). Wild Helianthus annuus L., H. petiolaris Nutt., and H. praecox Engl. ...
... Wild Helianthus annuus L., H. petiolaris Nutt., and H. praecox Engl. & Gray are sources of single dominant genes for single race resistance, while H. argophyllus T. & G. (silver leaf sunflower) is a source of a dominant gene for all known races of downy mildew (Miller and Gulya, 1988;Seiler, 1991;Miller et al., 2002;Jan and Gulya, 2006). One accession of H. argophyllus (ARG-1575, PI 468651) was collected on Daytona Beach, Volusia County, Florida, in October, 1980 by Gerald Seiler and Luka Cuk. ...
... The Pl arg gene is unlinked to other downy mildew resistance genes in sunflower. The other gene for downy mildew resistance to multiple races is PL 8, which was transferred from a H. argophyllus population from Texas and incorporated into inbred line RHA 340 (Miller and Gulya, 1988). ...
The genus Helianthus, besides constituting the basic genetic stock from which cultivated sunflower originated, continues to contribute unique characteristics for cultivated sunflower improvement. Genetic diversity of the wild species has allowed the crop to become and remain economically viable by contributing genes for resistance (tolerance) to pests and environmental stresses. However, there is a continued need to collect, maintain, and evaluate wild Helianthus germplasm for future utilization and enhancement of cultivated sunflower. The encroachment of humans into the habitats of some wild species is an urgent concern. A population of Helianthus argophyllus (ARG-1575, PI 468651) was collected on Daytona Beach, Volusia County, Florida, in October, 1980. This population contained genes that were used to develop an interspecific germplasm, ARG-1575-2 (PI 539913), which was resistant to all known races of downy mildew. Since only three plants were originally found, it appeared that this population was in imminent danger of being eliminated. Surprisingly, when this location was revisited in September, 2006, 50 plants were found scattered in an abandoned beachfront lot near the original collection site. Urbanization of this area is continuing, so it is hard to predict how long this population will survive. An abundance of seeds were collected and deposited in the sunflower germplasm collection at the USDA-ARS-NCRPIS, Ames, IA.
... • 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-DM12, HA-DM13, and HA-DM14 each pyramided two different downy mildew R genes and one rust R gene. • 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). ...
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.
... In Western Europe, where the climate is favorable for downy mildew, the genes Pl 1 and Pl 2 , from wild H. annuus, were rapidly incorporated into hybrid varieties and it became clear that the pathotype prevalent in Europe (100) was not the same as that in the United States (300) (Zimmer and Kinman, 1972). Between 1978 and1988, nearly all varieties carried these genes and the appearance, first in the United States and then in Europe, of new pathotypes not controlled by these genes (700, 703, 710) (Gulya et al., 1991) may well have been caused by the selection pressure applied on P. halstedii as well as by accidental downy mildew introductions in sunflower seed (Ahmed et al., 2012). Progress and Novinka and also some ecotypes of wild H. annuus and other annual Helianthus spp. ...
... Progress and Novinka and also some ecotypes of wild H. annuus and other annual Helianthus spp. (Miller and Gulya, 1988) provided effective resistance. However, in France, rapid appearance of further new pathotypes (304,314,334) provided confirmation that this was favored if all widely grown varieties carried the same resistance genes and that it was important to make a search for additional genes (Tourvieille de Labrouhe, 2003). ...
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.
... Sunflower wild species are also an important source of downy mildew resistance genes. Fourteen Pl genes (Pl 1 , Pl 2 , Pl 5 -Pl 8 , Pl 13 -Pl 18 , Pl 21 , and Pl Arg ) that were previously mapped to the sunflower genome can be traced to their wild origin, most of which were derived from wild annual species, especially H. annuus (Miller and Gulya 1987, 1988, 1991Seiler 1991Seiler , 2010Vear et al. 2008;Mulpuri et al. 2009;Hulke et al. 2010;). This species contributed five of the 14 Pl genes (Pl 1 , Pl 2 , Pl 6 , Pl 13 , and Pl 17 ) and is considered to be the most valuable source of Pl genes. ...
... Although many downy mildew resistance genes were identified from sunflower wild species [some of which were transferred into cultivated sunflower [ (Miller and Gulya 1987, 1988, 1991Seiler 1991;Rahim et al. 2002;Gulya 2005;Vear et al. 2008;Hulke et al. 2010;)], none of these genes are present in confection sunflower. Pl 19 is the first downy mildew R gene directly introduced from wild species into confection sunflower and is highly resistant to a wide range of P. halstedii races tested in the current study. ...
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.
... Berl. & de Toni (downy mildew) resistant (Race 4) lines illustrate this point (Miller and Gulya, 1988 ). The released germplasms consisted of two lines from wild H. annuus, three from wild H. praecox ssp. ...
... bSources:Putt and Sackston, 1963;Thompson et al., 1978;Quresh et al., 1989. c sources:Fick et al., 197 4;Thompson et al., 1978;Miller and Gulya, 1988;Tan et al., 1990. Verticillium dahliae Klebahn) is an important disease in sunflower. ...
The genus Helianthus is composed of 49 species and 19 subspecies with 12 annual and 37 perennial species. These diverse species represent considerable genetic variability which can be utilized for the improvement of cultivated sunflower. The taxonomy of Helianthus is somewhat confusing due to the complicated natural interspecific hybridization and different ploidy levels of several species. A germplasm collection of 2000 accessions, mostly annuals, has been assembled. Interspecific hybridization has become important as a means of introducing genetic variability into the cultivated sunflower. This has been facilitated by the use of embryo culture and chromosome doubling with colchicine to increase fertility. The wild species continue to serve as a source of cytoplasmic male sterility for cultivated sunflower. Molecular techniques of restriction endonucleases of mitochondrial DNA can be used to differentiate CMS sources. The greatest impact the wild species have made on cultivated sunflower has been in the area of genes for disease resistance and, to a lesser extent, resistance to insects. The recent discovery of genes for high tolerance to the disease Phomopsis/Diaporthe helianthi Munt. Cvet. is an excellent example. Considerable variability has been reported in oil content and fatty acid concentrations in the wild species as well as agronomic and morphologic traits of plant height, days to flowering and tolerances to stress, especially salt.
... Two DM R genes, Pl 17 in HA 458 and Pl 18 in HA-DM1, with known resistance to all new P. halstedii races occurring in North America, were recently fine mapped to sunflower chromosomes 4 and 2, respectively, with closely linked diagnostic DNA markers for both genes developed for facilitating marker-assisted selection (Gilley et al., 2020;Ma et al., 2019Ma et al., , 2020Qi et al., 2015. The inbred line RHA 340 carrying the Pl 8 gene was released in 1988 (Miller & Gulya, 1988) and is currently reported to be resistant to 178 of 185 P. halstedii isolates evaluated but susceptible to P. halstedii races 700 and 710 (Gilley et al., 2020), making it a good candidate for gene pyramiding with other Pl genes. The Pl 8 gene was previously mapped to sunflower chromosome 13 with available diagnostic single-nucleotide polymorphism (SNP) markers (Bachlava et al., 2011;Qi et al., 2017 (Bachlava et al., 2011;Qi et al., 2015. ...
Downy mildew (DM), caused by the obligate pathogen Plasmopara halstedii (Farl.) Berl. & de Toni, is a worldwide yield‐limiting disease of sunflower (Helianthus annuus L.). To obtain durable DM resistance in sunflower hybrids, there is a need to stack new resistance genes into the best available germplasm. The DM resistance genes Pl8, Pl17, and Pl18 were recently fine mapped to sunflower chromosomes 13, 4, and 2, respectively. The current study pyramided these genes into a single genotype by marker‐assisted selection. Three oilseed sunflower germplasms, HA‐DM9 (Reg. no. GP‐381, PI 700009), HA‐DM10 (Reg. no. GP‐379, PI 700004), and HA‐DM11 (Reg. no. GP‐380, PI 700005), are dual DM‐resistant germplasm lines developed and have been released by the USDA‐ARS, Sunflower and Plant Biology Research Unit in collaboration with the North Dakota Agricultural Experiment Station in 2021. The three lines, HA‐DM9 (Pl8Pl8/Pl17Pl17), HA‐DM10 (Pl8Pl8/Pl18Pl18), and HA‐DM11 (Pl17Pl17/Pl18Pl18), each stacked two different DM genes, providing broad resistance to all P. halstedii races identified in North America and Europe so far, and can be used in sunflower breeding programs to enhance DM resistance.
... The addition of these values for each set results in the 3-digit CVF. In addition to the nine differentials, isolates of P. halstedii were also inoculated into the inbred line RHA-340, which carries a highly effective genetic resistance against P. halstedii [28]. Seeds of each of the sunflower genotypes were germinated prior to inoculation with P. halstedii according to the methodology followed by our group [19]. ...
The management of downy mildew (Plasmopara halstedii) in sunflower, is heavily dependent on genetic resistance, whilst entomopathogenic fungi (EF) can reduce other sunflower diseases. In this work, we characterized P. halstedii from Spain and other countries collected in the past few years. Twenty-three races were identified (the most frequent in Spain being 310, 304, 705 and 715), with an increasing proportion of highly virulent races. Five isolates from countries other than Spain overcame the resistance in RHA-340. In addition, we assessed the efficacy of five EF against downy mildew and their effects on sunflower growth in axenic conditions. None of the entomopathogens reduced disease severity, nor did they have any effect on plant growth when applied together with P. halstedii. In contrast, three EF reduced some of the plant growth variables in the absence of the pathogen. Microbiological and molecular diagnostics suggest that the axenic system and the short experimental time used in this study did not favor the successful establishment of EF in the plants or their potential biocontrol effect. Our results show a shift in P. halstedii racial patterns and suggest that soil as a growth substrate and long infection times are needed for EF effectiveness against downy mildew.
... Resistance genes, denoted Pl genes, provide complete resistance to the pathogen. As the Pl genes are race-specific (Miller and Gulya 1988;Vear et al. 2008), there is a great probability that new races of downy mildew will overcome them in a relatively short period of time. Even though monogenic resistance is not durable, introgression of Pl genes is still among the most efficient methods of controlling downy mildew. ...
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.
... (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. ...
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.
... 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). ...
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.
... Wild annual sunflower species have been a bountiful source of Pl genes for DM resistance. Jan et al. (2004b) (Miller and Gulya, 1988). Helianthus argophyllus-derived germplasm ARG-1575-2 (Seiler, 1991b) carries the Pl arg locus conferring resistance to all known races of P. halstedii DM (Gascuel et al., 2015;Gilley et al., 2016). ...
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.
... Wild annual sunflower species have been a bountiful source of Pl genes for DM resistance. Jan et al. (2004b) (Miller and Gulya, 1988). Helianthus argophyllus-derived germplasm ARG-1575-2 (Seiler, 1991b) carries the Pl arg locus conferring resistance to all known races of P. halstedii DM (Gascuel et al., 2015;Gilley et al., 2016). ...
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 inbred line RHA 340 was released in 1988, and harbors the downy mildew resistance gene Pl 8 , which originated from the wild annual species Helianthus argophyllus (Miller and Gulya 1988). A recent study revealed that Pl 8 provides resistance against 96% of P. halstedii isolates collected from the north-central region of the USA in 2014 and 2015 (Gilley et al. 2016). ...
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.
... Here, it should be mentioned that genes for resistance to the new races were quickly found in wild species and promptly transferred into genotypes of the cultivated sunflower [55]. An international set of differential lines has been made which makes it possible to determine which downy mildew races are present in a certain region. ...
... H. argophyllus is a wild annual species that is mainly distributed in the sandy coastal plains of southern Texas (Rogers et al., 1982). It has been a valuable source of disease resistance genes for rust, downy mildew, and Sclerotinia (Miller and Gulya, 1988;Seiler, 1991Seiler, , 2010Gulya, 2005;Qi et al., 2016). Scientific attention has been given to H. petiolaris as the first cytoplasmic male-sterility (PET1 CMS) was discovered in this species and bred into cultivated sunflower (Leclercq, 1969). ...
Basal stalk rot (BSR), caused by Sclerotinia sclerotiorum, is a devastating disease in sunflower worldwide. The progress of breeding for Sclerotinia BSR resistance has been hampered due to the lack of effective sources of resistance for cultivated sunflower. Our objective was to transfer BSR resistance from wild annual Helianthus species into cultivated sunflower and identify the introgressed alien segments associated with BSR resistance using a genotyping-by-sequencing (GBS) approach. The initial crosses were made between the nuclear male sterile HA 89 with the BSR resistant plants selected from wild Helianthus argophyllus and H. petiolaris populations in 2009. The selected resistant F1 plants were backcrossed to HA 458 and HA 89, respectively. Early generation evaluations of BSR resistance were conducted in the greenhouse, while the BC2F3 and subsequent generations were evaluated in the inoculated field nurseries. Eight introgression lines; six from H. argophyllus (H.arg 1 to H.arg 6), and two from H. petiolaris (H.pet 1 and H.pet 2), were selected. These lines consistently showed high levels of BSR resistance across seven environments from 2012 to 2015 in North Dakota and Minnesota, USA. The mean BSR disease incidence (DI) for H.arg 1 to H.arg 6, H.pet 1, and H.pet 2 was 3.0, 3.2, 0.8, 7.2, 7.7, 1.9, 2.5, and 4.4%, compared to a mean DI of 36.1% for Cargill 270 (susceptible hybrid), 31.0% for HA 89 (recurrent parent), 19.5% for HA 441 (resistant inbred), and 11.6% for Croplan 305 (resistant hybrid). Genotyping of the highly BSR resistant introgression lines using GBS revealed the presence of the H. argophyllus segments in linkage groups (LGs) 3, 8, 9, 10, and 11 of the sunflower genome, and the H. petiolaris segments only in LG8. The shared polymorphic SNP loci in the introgression lines were detected in LGs 8, 9, 10, and 11, indicating the common introgression regions potentially associated with BSR resistance. Additionally, a downy mildew resistance gene, Pl17, derived from one of the parents, HA 458, was integrated into five introgression lines. Germplasms combining resistance to Sclerotinia BSR and downy mildew represent a valuable genetic source for sunflower breeding to combat these two destructive diseases.
... Wild annual sunflower species have been a bountiful source of Pl genes for DM resistance. Jan et al. (2004b) (Miller and Gulya, 1988). Helianthus argophyllus-derived germplasm ARG-1575-2 (Seiler, 1991b) carries the Pl arg locus conferring resistance to all known races of P. halstedii DM (Gascuel et al., 2015;Gilley et al., 2016). ...
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 8 was reported to be in a gene cluster on LG13, with Pl 5 and Pl 21 , whereas Pl 18 is, so far, the only gene located on LG2. The sunflower germplasms carrying Pl 8 (RHA 340) and Pl Arg (Arg1575-2) were released in 1988 and 1991, respectively (Miller and Gulya 1988;Seiler 1991). The gene Pl Arg still effectively confers resistance to all of the P. halstedii races identified so far in the USA and France, and Pl 8 confers resistance to 98 % of the P. halstedii isolates Gascuel et al. 2014;Gilley et al. 2015). ...
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.
... Pl 5 shows resistance to race 700 (17). Pl 6 , Pl 7 , and Pl 8 confer resistanceagainst races 100, 300, 310, 330, and 700 (18,19). Resistance to races 310, 330, and 300 is conferred by Pl 9 , Pl 10 , and Pl 11 , respectively (19). ...
Background:
Downy mildew caused by Plasmopara halstedii is a devastating disease in sunflower worldwide. Several dominant resistance genes designated as Pl have been identified and linked molecular markers have been demonstrated. However, no information on theresistance genes is available forIranian lines.
Objectives:
The presence of three map-based molecular markers previously proved to be linked to different resistance genes were evaluated in sunflower inbred lines.
Materials and methods:
Using PCR-based and CAPS molecular markers, 26 sunflower inbred lines with different responses to P. halstedii race 100 were used to detect the presence of three resistance loci including Pl1 , Pl6 and Pl13 within the lines.
Results:
Molecular marker linked to Pl13 was present in some of the sunflower lines but was not correlated with the phenotypic reaction of the lines to race 100. Despite the use of three markers linked to Pl6 , PCR failed to amplify any corresponding product. This data may suggest that none of the genotypes possessed Pl6 locus. Pl1 -linked cleaved amplified polymorphic sequences (CAPS) were present in several resistance lines and effectively differentiated susceptible and resistant sunflower lines.
Conclusions:
Applicability of molecular markers in breeding programs revisited in disease management.
... Downy mildew can be controlled by single, race-specific major dominant genes. Multi-race resistant germplasm and single-race resistant germplasms from wild sunflower species have been developed (Miller and Gulya, 1988;Tan et al., 1992;Jan et al., 2004a). Wild H. annuus, H. petiolaris, H. tuberosus, and H. praecox ssp. ...
Genebanks are a rich source of genetic diversity that can be readily exploited for crop improvement. The USDA-ARS established a cultivated sunflower germplasm collection at the National Plant Germplasm System, North Central Regional Plant Introduction Station at Ames, Iowa in1948. A wild Helianthus germplasm collection was established at the USDA-ARS Bushland, Texas station in 1976. Presently, both collections are maintained and managed at Ames, Iowa. The genus Helianthus consists of 52 species and 19 subspecies, with 14 annual and 38 perennial species. Over 30 explorations in the past 35 years have resulted in the assemblage of a wild sunflower collection that is the most complete in the world. Currently, the sunflower collections contain 4087 accessions: 1886 cultivated H. annuus accessions and 2201 wild accessions of which 1359 accessions are annual and 842 are perennial species. This germplasm is an important current and future genetic resource to combat emerging pests and environmental challenges, helping to maintain sunflower as a viable major global oilseed crop and preserve it for future generations.
... Crown rust resistance (Hoffman et al., 2006) and yield improvement (Takeda and Frey, 1976) Corylus americana Marshall Eastern fi lbert blight resistance (Thompson et al., 1996) Helianthus anomalus S. F. Blake Fertility restoration (Seiler, 1991a) Helianthus argophyllus Torr. & A. Gray Downy mildew resistance (Hulke et al., 2010;Miller and Gulya, 1988), disease resistance (Jan et al., 2004), and fertility restoration (Seiler, 1991a) Helianthus bolanderi A. Gray Genetic stock (Jan, 1992) and fertility restoration (Seiler, 1991a) Helianthus debilis Nutt. ...
The use of crop wild relatives (CWRs) in breeding is likely to continue to intensify as utilization techniques improve and crop adaptation to climate change becomes more pressing. Significant gaps remain in the conservation of these genetic resources. As a first step toward a national strategy for the conservation of CWRs, we present an inventory of taxa occurring in the United States, with suggested prioritization of species based on potential value in crop improvement. We listed 4600 taxa from 985 genera and 194 plant families, including CWRs of potential value via breeding as well as wild species of direct use for food, forage, medicine, herb, ornamental, and/or environmental restoration purposes. United States CWRs are related to a broad range of important food, forage and feed, medicinal, ornamental, and industrial crops. Some potentially valuable species are threatened in the wild, including relatives of sunflower (Helianthus annuus L.), walnut (Juglans regia L.), pepo squash (Cucurbita pepo L.), wild rice (Zizania L.), raspberry (Rubus idaeus L.), and plum (Prunus salicina Lindl.), and few accessions of such taxa are currently conserved ex situ. We prioritize 821 taxa from 69 genera primarily related to major food crops, particularly the approximately 285 native taxa from 30 genera that are most closely related to such crops. Both the urgent collection for ex situ conservation and the management of such taxa in protected areas are warranted, necessitating partnerships between concerned organizations, aligned with regional and global initiatives to conserve and provide access to CWR diversity.
... The rapid changes that occur in its virulence represent a continuous Genetics and Genomics Applied to Sunflower Breeding 69 threat to the effectiveness of existing rust-resistance inbred lines and hybrids. Several genes conferring resistance to rust have been identified in sunflower including R 1 , R 2 , R 3 , R 4 , R 5 , Pu 6 , R adv , R 11 and R 12 (Putt and Sackston 1957;Miah and Sackston 1970;Miller and Gulya 1988;Yang 1989;Lawson et al., 1998;Gong et al., 2013), but only a few of them have been genetically characterized, mapped and linked to molecular markers. In addition, several inbred lines and interspecific germplasm lines were reported to have resistance to different rust races (Quresh et al., 1993;Bulos et al., 2012). ...
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.
... Another Rf gene, Msc 1 , was mapped to LG 12 of the map of Gentzbittel et al. (1999). A third Rf gene, Rf 3 , from RHA 340, which was derived from the cross HA 89*3 9 H. argophyllus 415 (Miller and Gulya 1988), was mapped to LG 7 of the SSR map (Abratti et al. 2008). Rf 4 , from wild species H. maximiliani accession 1631 for the CMS GIG1, was mapped on LG 3 of the SSR genetic map (Feng and Jan 2008). ...
The inheritance of a previously identified dominant Rf gene in the confection sunflower line RHA 280 has been determined and designated as Rf
3
. This study reports the mapping of the Rf
3
locus using an F2 population of 227 individuals derived from CMS HA 89-3149 × RHA 280. Bulked segregant analysis with 624
pairs of simple sequence repeat (SSR) primers and sequence tagged site (STS) primers identified two polymorphic SSR markers
each of linkage groups (LGs) 7 and 11 from a previous map. Results on 90 F2 individuals with 42 polymorphic markers of LGs
7 and 11 indicated that the Rf
3
gene was linked with eight markers on LG 7, including five SSR markers (ORS328, ORS331, ORS928, ORS966, and ORS1092) and
three expressed sequence tag (EST)-SSR markers (HT619-1, HT619-2, and HT1013). Further analysis of the total F2 population
of 227 individuals identified a co-dominant marker, ORS328, linked to Rf
3
at a genetic distance of 0.7 cM on one side, and a female-dominant marker HT1013 at 12.6 cM proximal to Rf
3
on the other side; a genetic distance of 47.1 cM for LG 7 was covered. This is the first report of an Rf gene from the confection sunflower. The closely linked marker to Rf
3
will facilitate marker-assisted selection, and provide a basis for cloning of this gene.
... The progeny was subjected to several backcrosses with recurrent parental lines. Ha-26 was also improved by introducing resistance to Plasmopara halstedii from Ha-335, another source of Pl6 (Miller and Gulya, 1988, 1991), noted as Ha-26(R). Screening and selection of resistant individuals after crossings were performed by the whole seedling immersion method. ...
RÉSUMÉ
Le but de cette étude est l’application des marqueurs PCR déjà publiés et le développement des nouveaux dans l’évaluation de résistance du tournesol à la rouille. Vingt lignes cultivées de tournesol ont été examinées. La résistance de plantes à la rouille est déterminée par la méthode d’immersion totale de semailles. Après l’isolation de A.D.N. génomique de première paire de feuilles, le polymorphisme a été examiné par application des marqueurs RAPD, SSR, et quelques marqueurs déjà publiés pour la résistance aux maladies.
La présence des marqueurs Ha-NBS 7/R, Ha-NBS 8/R et Ha-NBS 9/R, dans les donneurs de gène P16 (Ha-335, JM-8) et les lignes résistantes (Ha-26, G12, G10, G11), obtenues par croisement de lignes donneurs et lignes irrésistibles, confirme que l’application de “primer” HAP3 peut être efficace pour détecter le gène P16.
Le polymorphisme A.D.N qui est en corrélation avec le trait de résistance à la rouille, est dépisté par l’application d’un RAPD “primer” (fragment UBC 119; 900-1000 bp) et d’un SSR “primer” (fragment ORS37; 900-700 bp). Les deux fragments multipliés se sont avérés chez 50% de génotypes résistants. Le fragment SSR qui n’a pas été attendu est purifié, cloné et disposé en séquence. Les résultats indiquent que ce segment ne fait pas partie d’une séquence codée. Pour multiplier ce fragment un “primer” spécifique a été créé, et les recherches d’hérédité du marqueur SCAR sont en cours. Aucun marqueur appliqué ne s’est manifesté dans tous les génotypes résistants.
Les résultats obtenus sont aussi utilisés pour calculer la distance génétique entre les génotypes (“simple matching” coefficient) et construire de “dendrogramme” (la méthode UPGMA) afin de sélectionner les lignes de croisement qui seront mises en oeuvre dans les recherches futures.
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).
Phomopsis stem canker of cultivated sunflower (Helianthus annuus L.) can be caused by multiple necrotrophic fungi in the genus Diaporthe, with Diaporthe helianthi and D. gulyae being the most common causal agents in the United States. Infection begins at the leaf margins and proceeds primarily through the vasculature, progressing from the leaf through the petiole to the stem resulting in formation of brown stem lesions centered around the petiole. Sunflower resistance to Phomopsis stem canker is quantitative and genetically complex. Due to the intricate disease process, resistance is possible at different stages of infection and multiple forms of defense may contribute to the overall level of quantitative resistance. In this study, sunflower lines exhibiting field resistance to Phomopsis stem canker were evaluated for stem and leaf resistance to multiple isolates of both D. helianthi and D. gulyae in greenhouse experiments and responses to the two species were compared. Additionally, selected resistant and susceptible lines were evaluated for petiole transmission resistance to D. helianthi. Lines with distinct forms of resistance were identified and results indicated that responses to stem inoculation were strongly correlated (Spearman's coefficient 0.598, P < 0.001) for the two fungal species while leaf responses were not (Spearman's coefficient 0.396, P = 0.076). These results provide a basis for genetic dissection of distinct forms of sunflower resistance to Phomopsis stem canker and will facilitate combining different forms of resistance to potentially achieve durable control of this disease in sunflower hybrids.
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
Key message
Discovery of two rust resistance genes, R17 and R18, from the sunflower lines introduced from South Africa and genetic mapping of them to sunflower chromosome 13.
Abstract
Rust, caused by the fungus Puccinia helianthi Schw., is one of the most serious diseases of sunflower in the world. The rapid changes that occur in the virulence characteristics of pathogen populations present a continuous threat to the effectiveness of existing rust-resistant hybrids. Thus, there is a continued need for the characterization of genetically diverse sources of rust resistance. In this study, we report to identify two new rust resistance genes, R17 and R18, from the sunflower lines, KP193 and KP199, introduced from South Africa. The inheritance of rust resistance was investigated in both lines using two mapping populations developed by crossing the resistant plants selected from KP193 and KP199 with a common susceptible parent HA 89. The F2 populations were first genotyped using genotyping by sequencing for mapping of the rust genes and further saturated with markers in the target region. Molecular mapping positioned the two genes at the lower end of sunflower chromosome 13 within a large gene cluster. Two co-segregating SNP markers, SFW01497 and SFW08875, were distal to R17 at a 1.9 cM genetic distance, and a cluster of five co-segregating SNPs was proximal to R17 at 0.7 cM. R18 co-segregated with the SNP marker SFW04317 and was proximal to two cosegregating SNPs, SFW01497 and SFW05453, at 1.9 cM. These maps provide markers for stacking R17 or R18 with other broadly effective rust resistance genes to extend the durability of rust resistance. The relationship of the six rust resistance genes in the cluster was discussed.
Root and tuber crops are staples in diets across the world. They are favored due to a large yield associated with the small acreage needed to grow. Generally, they tend to be fairly robust to insect and disease pests and have historically been used as starvation food. Some root and tuber crops, such as potato, sweet potato, or cassava, are the primary source of daily calories for many cultures worldwide. Some tuber crops are only partially domesticated, facilitating the use of crop wild relatives (CWR). Many different cultures have their favorite root crops, but culinary preparation techniques often allow for different tubers to be used, making the acceptance of these crops fairly rapid. Here, we explore the origins and uses of eight tuber and root crops that are important to world diets and have many related wild species in North America.
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.
Key message:
A novel rust resistance gene, R15, derived from the cultivated sunflower HA-R8 was assigned to linkage group 8 of the sunflower genome using a genotyping-by-sequencing approach. SNP markers closely linked to R15were identified, facilitating marker-assisted selection of resistance genes. The rust virulence gene is co-evolving with the resistance gene in sunflower, leading to the emergence of new physiologic pathotypes. This presents a continuous threat to the sunflower crop necessitating the development of resistant sunflower hybrids providing a more efficient, durable, and environmentally friendly host plant resistance. The inbred line HA-R8 carries a gene conferring resistance to all known races of the rust pathogen in North America and can be used as a broad-spectrum resistance resource. Based on phenotypic assessments of 140 F2individuals derived from a cross of HA 89 with HA-R8, rust resistance in the population was found to be conferred by a single dominant gene (R15) originating from HA-R8. Genotypic analysis with the currently available SSR markers failed to find any association between rust resistance and any markers. Therefore, we used genotyping-by-sequencing (GBS) analysis to achieve better genomic coverage. The GBS data showed that R15was located at the top end of linkage group (LG) 8. Saturation with 71 previously mapped SNP markers selected within this region further showed that it was located in a resistance gene cluster on LG8, and mapped to a 1.0-cM region between three co-segregating SNP makers SFW01920, SFW00128, and SFW05824 as well as the NSA_008457 SNP marker. These closely linked markers will facilitate marker-assisted selection and breeding in sunflower.
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.
HA-DM1 (Reg. No. GP-335, PI 674793) sunflower (Helianthus annuus L.) germplasm was developed and released cooperatively by the USDA-ARS, Sunflower and Plant Biology Research Unit and the North Dakota Agricultural Experiment Station in 2015. HA-DM1 is a BC 2 F 4 –derived oilseed maintainer line from the cross HA 89*2/NMS HA 89/Helianthus argophyllus PI 494573, selected for resistance to downy mildew (DM) [caused by Plasmopara halstedii (Farl.) Berl. et de Toni], a destructive disease in sunflower. The DM resistance in HA-DM1 originated from wild H. argophyllus accession PI 494573 and is conditioned by a single dominant gene designated Pl 18. Pl 18 has been mapped to linkage group 2 of the sunflower genome and is independent of all known identified DM resistance genes in sunflower. HA-DM1 has resistance to all P. halstedii races identified in the United States to date, providing a potential new source for resistance to emerging virulent races of P. halstedii in sunflower in North America and around the world.
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.
Among the factors hindering the conservation of crop genetic resources is a lack of essential information regarding this diversity. Questions include: (a) what is the status of diversity in our food systems, and where are the greatest vulnerabilities?, (b) where can genetic diversity be found that can be useful in increasing productivity and mitigating these vulnerabilities?, (c) is this genetic diversity available in the present and in the long term?, and (d) what steps are needed to improve the ability for researchers to access genetic resources critical for present and future crop improvement? This thesis aims to contribute to the knowledge required to answer these questions through an exploration of the need for, potential of, challenges and constraints regarding, and necessary steps to enhance the conservation and use of crop genetic diversity.
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.
Key message:
The rust resistance gene R 2 was reassigned to linkage group 14 of the sunflower genome. DNA markers linked to R 2 were identified and used for marker-assisted gene pyramiding in a confection type genetic background. Due to the frequent evolution of new pathogen races, sunflower rust is a recurring threat to sunflower production worldwide. The inbred line Morden Cross 29 (MC29) carries the rust resistance gene, R 2 , conferring resistance to numerous races of rust fungus in the US, Canada, and Australia, and can be used as a broad-spectrum resistance resource. Based on phenotypic assessments and SSR marker analyses on the 117 F2 individuals derived from a cross of HA 89 with MC29 (USDA), R 2 was mapped to linkage group (LG) 14 of the sunflower, and not to the previously reported location on LG9. The closest SSR marker HT567 was located at 4.3 cM distal to R 2 . Furthermore, 36 selected SNP markers from LG14 were used to saturate the R 2 region. Two SNP markers, NSA_002316 and SFW01272, flanked R 2 at a genetic distance of 2.8 and 1.8 cM, respectively. Of the three closely linked markers, SFW00211 amplified an allele specific for the presence of R 2 in a marker validation set of 46 breeding lines, and SFW01272 was also shown to be diagnostic for R 2 . These newly developed markers, together with the previously identified markers linked to the gene R 13a , were used to screen 524 F2 individuals from a cross of a confection R 2 line and HA-R6 carrying R 13a . Eleven homozygous double-resistant F2 plants with the gene combination of R 2 and R 13a were obtained. This double-resistant line will be extremely useful in confection sunflower, where few rust R genes are available, risking evolution of new virulence phenotypes and further disease epidemics.
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.
ResearchGate has not been able to resolve any references for this publication.