EXPLORATION FOR WILD HELIANTHUS ANOMALUS AND H. DESERTICOLA IN THE DESERT SOUTHWEST USA

Authors: Seiler, Gerald; Brothers, Mary

Submitted to: Proceedings Sunflower Research Workshop
Publication Type: Proceedings
Publication Acceptance Date: 3/1/2003
Publication Date: 3/1/2003
Citation: SEILER, G.J., BROTHERS, M.E. EXPLORATION FOR WILD HELIANTHUS ANOMALUS AND H. DESERTICOLA IN THE DESERT SOUTHWEST USA. Available from: http://www.sunflowernsa.com/research_statistics/research_workshop/documents/90.pdf PROCEEDINGS SUNFLOWER RESEARCH WORKSHOP [2003]

Interpretive Summary: The disappearance of habitat for several wild sunflower species is of concern for the long-term survival of the sunflower industry because wild species are the ancestors of the crop. The narrow genetic base of cultivated sunflower has been broadened by the infusion of genes from the wild species, which have provided a continued source of desirable agronomic traits. Therefore, it is imperative that as many natural populations of wild species as possible be collected and preserved in germplasm collections for future use. There has been an increased interest in breeding sunflower for drought tolerance. Helianthus anomalus (anomalous sunflower) and H. deserticola (desert sunflower) are excellent candidates for drought tolerance genes based on their adaptation to desert environments. Unfortunately, due to the demand for the seed of these species and the difficulties of regenerating the original populations, seed has not been available for research for almost 20 years. The objective of the present study was to undertake an exploration to the desert southwest US to collect seeds of the two desert species for the USDA-ARS sunflower germplasm collection and make them available for further research. The sunflower exploration covered 2550 miles in Utah, Arizona, and Nevada, during September of 2000. It was an extremely dry year, with no evidence of either species being present in many of the fragile sandy habitats visited 20 years ago. For whatever reason, only three populations had plants with seeds for collection in 2000, one population of the desert sunflower and two populations of the anomalous sunflower. The desert sunflower population had a typical oil content of 33%, compared to 45% for cultivated sunflower, while the populations of the anomalous sunflower had a very high oil content of 43 to 46%, the highest ever observed in any wild sunflower species. The fatty acid profile of the anomalous sunflower was high in linoleic acid content for a desert environment, approaching 70%, while the linoleic acid concentration in the desert sunflower of 54% is more typical of what one would expect to observe in a desert environment. The saturated palmitic and stearic fatty acids in anomalous sunflower were about 25% less than in cultivated sunflower oil. There appears to be adequate variability in this wild species to breed for a reduced level of the saturated fatty acids in cultivated sunflower oil. The anomalous sunflower has the largest seed and the highest oil concentration of any of the wild sunflower species. This will facilitate the breeding process when the wild germplasm is introgressed into cultivated germplasm for further screening for drought tolerance traits. The addition of these populations of wild species to the wild sunflower germplasm collection will insure their preservation for the future, and will greatly increase the available genetic diversity for improving the cultivated sunflower, keeping it a viable and competitive global crop.

Technical Abstract: The genus Helianthus is composed of 50 species and 19 subspecies with 13 annual and 37 perennial species. The narrow genetic base of cultivated sunflower has been broadened by the infusion of genes from the wild species, which have provided a continued source of desirable agronomic traits. There has been an increased interest in breeding sunflower for drought tolerance. Helianthus anomalus and H. deserticola are excellent candidates for drought tolerance genes based on their adaptation to desert environments. Unfortunately, due to the demand for the seed of these species and the difficulties of regenerating the original populations, seed has not been available for research for almost 20 years. Due to the disappearance of habitat for several wild sunflower species, it its imperative that as many natural populations as possible be collected and preserved in germplasm collections for future use. The objective of the present study was to undertake an exploration to the desert southwest US to collect seeds of the two desert species, adding them to the USDA-ARS sunflower germplasm collection and making them available for further research. The sunflower exploration took place from September 16 to September 23, 2000. The exploration covered 2550 miles in three states, Utah, Arizona, and Nevada. It had been an extremely dry year in most of the areas explored, with no evidence of the species being present in many of the fragile sandy habitats. For whatever reason, only three populations had plants with seeds for collection in 2000, one population of H. deserticola and two H. anomalus populations. The seed samples were deposited at the USDA-ARS North Central Regional Plant Introduction Station, Ames, IA where they will be maintained and distributed. Oil content and fatty acid composition were determined on the collected populations. The H. deserticola population had a typical oil content of 33%, while the populations of H. anomalus had very high oil content of 43 and 46% respectively, the highest ever observed in any wild sunflower species. The fatty acid profile of H. anomalus had a high linoleic acid concentration for a desert environment, approaching 70%. A linoleic acid concentration of 54% in H. deserticola is more typical of what one would expect to observe in a desert environment. The saturated palmitic and stearic fatty acids in H. anomalus averaged 8.4%, about 25% less than in cultivated sunflower oil. Helianthus anomalus has the largest seed and the highest oil concentration of any of the wild sunflower species. This will facilitate the breeding process when the wild germplasm is introgressed into cultivated germplasm for further screening for drought tolerance traits.