Location: Sunflower and Plant Biology Research2012 Annual Report
1a. Objectives (from AD-416):
1. Collect and evaluate wild and interspecific germplasm for useful agronomic traits. 2. Introgress useful genes into cultivated sunflower through interspecific hybridization and release the enhanced germplasm. 3. Develop DNA markers and apply them to genetic studies and marker-assisted selection.
1b. Approach (from AD-416):
We will collect nine underrepresented wild Helianthus species to fill gaps in the sunflower collection. Wild species will be evaluated for various agronomic traits, such as insect and disease resistance, saturated fatty acid content, cytoplasmic male sterility, and fertility restoration. DNA markers will be identified and used to reveal genetic diversity in the wild Helianthus collection. Once useful germplasm is identified, we will introgress the genes of interest into cultivated sunflower through interspecific hybridization. We will concentrate on transfer of Sclerotinia head and stalk rot resistance genes from wild perennial species into cultivated sunflower. Other traits we will identify and transfer are resistance to sunflower rust, downy mildew, and insects. Additional EST-based and SNP DNA markers will be developed for further saturation of the sunflower genetic map, and markers tightly linked to traits such as resistance to downy mildew, rust, and Sclerotinia, as well as to fertility restoration, will be used to expedite the process of sunflower germplasm enhancement via marker-assisted selection. We will use association mapping to identify DNA markers associated with insect resistance. BAC and BIBAC clones will be used to identify trisomics for the purpose of assigning individual linkage groups of the sunflower genetic map to single chromosomes of cultivated sunflower. BSL-1, 7/3/07.
3. Progress Report:
Two hundred populations of three perennial wild sunflower species were analyzed for oil concentration and fatty acid composition. One of these species, the rare Eggert’s sunflower, had a fatty acid profile of particular interest where one population had a high linoleic acid concentration of 78%. It is very unusual for species from the southeast US to have such high levels of linoleic acid. Sclerotinia-resistant wild perennial species sources, including interspecific amphiploids, hexaploid H. californicus and H. schweinitzii, diploid H. nuttallii, H. maximiliani, H. giganteus, and H. grosseserratus, have been crossed with cultivated lines HA 410 or HA 451 and tested in replicated field tests in 2009 and 2011 for head and stalk rot resistance, which indicated moderate to good resistance. A genomic in situ hybridization technique distinguishing chromosomes of the perennials and cultivated sunflower has been developed providing a new tool for studying gene transfer. This technique indicated a higher frequency of gene introgression from diploid perennials than from hexaploid or interspecific amphiploids. New interspecific lines were developed using perennial accessions of H. salicifolius, H. hirsutus, H. occidentalis, H. divaricatus, and H. resinosus to further diversify the Sclerotinia resistance gene pool. The development of Sclerotinia stalk rot resistance from wild annual sunflower species continued. During the winter of 2011 and spring 2012, a total of 4,340 plants from the BC2F2 populations were screened in the greenhouse and 250 of the most resistant plants were advanced for field testing to validate the greenhouse results during the 2012 field season. Molecular mapping of rust resistance genes continued. The rust resistance genes in the lines Rf ANN-1742 and RHA 464 were designated as R11 and R12 and were mapped to sunflower linkage groups 13 and 11, respectively. The rust resistance gene R11 is tightly linked to a male-fertility restorer gene, RF5, in a coupling phase. To transfer rust resistant genes (R2, R4, and R5) into confection sunflower breeding material, homozygous BC3F2 and BC4F2 plants were obtained and will be tested in 2012 to observe their agronomic performance. Integration of classical genes onto the sunflower molecular map continues with the mapping of the newly identified vigor restoration gene, a recessive white-cotyledon gene, three nuclear male sterile-genes, a gene cluster resistant to multiple races of rust in germplasm line HA-R4, a gene cluster conditioning resistance to multiple races of downy mildew and rust in germplasm line TX16, and rust resistance, and the hypocotyl color gene in germplasm line PH3. A high-density genetic map of sunflower with 2,178 SNP loci was completed. This map combines two disease resistance genes, one for the rust R-gene R12 and the other for the downy mildew (DM) PLarg gene. Progress was made in the genetic and mapping studies of new DM resistance genes. Four mapping populations were developed for new DM resistance genes using lines HA 458, RHA 468, 803-1, and an introgression line with the resistance gene derived from wild annual Helianthus argophyllus.
1. Polyunsaturated fatty acid sunflower oil. Traditional sunflower oil is nutritious containing zero trans fats, low saturated fatty acids, high polyunsaturated linoleic acid, high vitamin E and contributes to improved human health. Genetic diversity is the key to the survival of any crop with sunflower being unique in that it originated in southeastern US and is represented by 52 different species. ARS scientists in Fargo, North Dakota analyzed 200 populations of wild sunflower species for fatty acid composition in the oil. A population of Eggert’s sunflower had a particularly high polyunsaturated fatty acid concentration, unusual for a species from the southeast US. Production of high polyunsaturated sunflower oil in the south would expand the potential production of sunflower, provide crop rotation choices for producer, and increase the availability of sunflower oil to consumers.
2. A durable sunflower rust resistance gene. Sunflower is an important oil and confection seed crop in the US. Sunflower production in North America is constantly being threatened by the development of new virulent races of sunflower rust. ARS scientists in Fargo, North Dakota, discovered a novel rust resistance gene, termed R11, from a genetic line of sunflower that provides resistance to the newly emerged virulent rust races. This multi-strain rust resistant gene has been mapped on the public sunflower map using two DNA markers that will allow breeders to improve rust resistance in commercial hybrid sunflower. Enhanced resistance to devastating diseases like rust will sustain sunflower production in large portions of the US, improve net returns for sunflower growers, provide food processors with abundant source of healthy oil, and American consumers with sunflower seeds for direct consumption.
3. Molecular mapping of a novel rust resistance gene in sunflower. Sunflower is an important oil and confection seed crop in the US. Change in infectiousness of the sunflower rust populations in North America has rendered most of the commercial hybrids susceptible to new strains. Molecular markers are a new tool that can be used for marker assisted breeding. ARS scientists in Fargo, North Dakota, discovered the R12 gene that confers resistance to the most predominant and most virulent rust races in the US Northern Great Plains. Discovery of the R12 novel rust resistance locus in sunflower and associated markers will potentially support the introduction of the rust resistance gene, R12, into sunflower breeding lines. Ultimately, durable rust resistance will reduce chemical applications and will sustain and improve production in an environmentally friendly manner, and will enhance net returns for sunflower growers and processers.
4. Mapping of a durable downy mildew resistance gene in sunflower. Sunflower is important oil and confection seed crop in the US, but it is continually challenged by fungal pathogens that are changing in virulence over time. This results in most of the commercial hybrids being susceptible to the new virulent races. ARS scientists in Fargo, North Dakota, discovered a downy mildew gene (PL16) from a germplasm line (HA-R4) resistant to the predominant races of downy mildew and all new virulent races. This gene was characterized, and is identified by a closely linked marker which will facilitate marker assisted selection in sunflower resistance breeding. Use of molecular tools will expedite the breeding process to incorporate genetic resistance into sunflower reducing the application of chemicals and their environmental impact and enhancing net returns for sunflower growers and processers.
Lawson, W., Jan, C., Shatte, T., Smith, L., Kong, G., Kochman, J. 2011. DNA markers linked to the R2 rust resistance gene in sunflower (Helianthus annuus L.) facilitate anticipatory breeding for this disease variant. Molecular Breeding. 28:569-576.