Location: Sunflower and Plant Biology Research2009 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.
3. Progress Report
An exploration covering 5200 miles was undertaken in Texas, New Mexico, and Arizona collecting 20 populations of H. ciliaris, 8 populations of H. laciniatus, 3 populations of H. arizonensis, and 2 populations of wild H. annuus. These collections fill a gap in the wild sunflower collection for future improvement of cultivated sunflower. In addition, over 200 populations of wild sunflower were analyzed for oil concentration and fatty acid composition. They were represented by 5 annual and 12 perennial species. Of particular interest was the high linoleic acid concentration of 81.5% in one population of Helianthus porteri, the highest ever reported for a wild annual species. One population of H. anomalous from the desert southwest in Utah had an oil concentration of 44.5%, the highest ever reported for any wild sunflower species. Successful interspecific crosses were made with 4 annual and 1 perennial species. The project on Sclerotinia resistant germplasm development utilizing wild Helianthus species continued. Several crosses between cultivated lines and Sclerotinia stalk rot and head rot resistant wild perennial species were backcrossed to advanced generations. In 2009 we evaluated 155 progeny families in field tests for head rot and 321 families for stalk rot, both at Carrington, ND. The integration of classical genes onto the molecular map is in progress. We completed the mapping of fertiliy restoration genes Rf3 and Rf4, a downy mildew resistance gene in line GAR-5, and one vigor restoration gene. Additional Rf genes for the cms GIG2 male-sterile cytoplasm were identified. Mapping of one NMS gene causing both male and female sterility and gene clusters for multiple races of downy mildew and rust resistance in HAR4 and HAR5 are in progress. Amphiploid seeds of five crosses with cultivated line P21 and one intercrossed amphiploid of H. divaricatus and H. grosseserratus have been increased. These amphiploids have resistance genes to both stem and head rot and can be quickly incorporated into cultivated lines by conventional breeding. In 2009 we used a core set of 1700 sunflower SSR DNA markers to establish that the gene expressing the high-oleic acid trait in a line from wild H. giganteus is the same gene responsible for the high-oleic trait in the traditional Pervenets line. The molecular mapping of rust resistance genes R4 in sunflower line HAR3 and R5 in HAR2 line was initiated, and the DNA fingerprinting of 46 wild annual and 106 perennial accessions was begun. Eight recombinant lines resistant to sunflower stalk rot and head rot, together with their parents and 14 testcrosses, were reevaluated under field conditions. We advanced the recombinant inbred line population from the cross HA441 and RHA439 to the F5 generation, and the recombinant inbred line population from the cross HA 234 and RHA 271 was advanced to the F7:8 generation. In addition, a new project was initiated for transferring sunflower Sclerotinia resistance genes from wild annual species to cultivated sunflower. Plants resistant to stalk rot were selected from H. argophyllus, H. exilis, H. praecox, H. debilis, and H. petiolaris and were crossed to inbred lines of nmsHA89.
1. Exploration for wild sunflower species. Sunflower production continues to be challenged by several insect and disease pests while its production is also being shifted to marginal areas, further challenging the crop. Genetic diversity is the key to an adaptable crop to stresses such as diseases, insect pests, and drought. Some species of wild sunflowers are underrepresented in the sunflower collection at the USDA-ARS North Central Plant Introduction Station in Ames, Iowa. A comprehensive exploration plan has been developed to add more wild sunflower populations to the sunflower collection. The Sunflower Research Unit in Fargo, North Dakota, undertook an exploration for wild sunflower germplasm from the southwest US covering 5200 miles in Texas, New Mexico, and Arizona, collecting 20 populations of Helianthus ciliaris, 8 populations of Helianthus laciniatus, 3 populations of Helianthus arizonensis, and 2 populations of wild Helianthus annuus. The value of this germplasm is the potential drought tolerance of the latter three of these species. These collections fill a gap in the wild sunflower germplasm collection, making these species available to evaluate for useful traits that can be utilized for the improvement of cultivated sunflower.
2. Inheritance of sunflower downy mildew resistance. Downy mildew is a serious pathogen of sunflower that often strikes early in the growing season, especially under cool, damp environments. Sunflower line HA-R5 confers resistance to nine races of this pathogen and is a good potential parental source for incorporation of downy mildew resistance into commercial sunflower hybrid seed. Scientists at the ARS Sunflower Research Unit in Fargo, ND, determined the inheritance of the downy mildew resistance gene in HA-R5, designated as Pl-13, and mapped it to linkage group 1 of the public sunflower SSR genetic map, close to two DNA SSR markers. These closely linked markers to the Pl-13 gene provide a valuable basis for marker-assisted selection in a sunflower breeding program for developing downy mildew resistant lines.
3. High oil content and high linoleic acid content in wild sunflower species. Sunflower oil and oil quality determine its potential uses and are key issues in sunflower breeding. The search for new sources of these traits is ongoing, with the wild sunflower species offering considerable genetic diversity for selecting these traits. Scientists at the Sunflower Research Unit in Fargo, North Dakota, analyzed over 200 populations of wild sunflower, represented by 5 annual and 12 perennial species, for oil concentration and fatty acid composition. Of particular interest was the high linoleic acid concentration of 81.5% in one population of Helianthus porteri, the highest ever reported for a wild annual species. It is very unusual for species from the southeast US to have such high levels of linoleic acid. One population of Helianthus anomalous from the desert southwest in Utah had an oil concentration of 44.5%, the highest report for any wild sunflower species. Knowledge of the oil and oil quality traits will facilitate the use of the wild species in breeding programs for these and other traits.
Feng, J., Jan, C.C. 2008. Introgression and molecular tagging of Rf4, a new male fertility restoration gene from wild sunflower Helianthus maximiliani L. Theoretical and Applied Genetics. 117:241-249.