Collection and Evaluation of Helianthus Verticillatus, An Endemic Sunflower of the Southeast US.

The genus Helianthus comprises 51 species, 14 annual and 37 perennial, all native to North America. 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. Whorled sunflower, Helianthus verticillatus Small, is a diploid perennial species first collected in western Tennessee in 1898 and not seen again until it was rediscovered a century later in 1998 near the original site. It occurs in low moist prairie soils in Alabama, Georgia, and Tennessee. Unfortunately, no achenes of this rediscovered species were previously available for evaluation for oil concentration and fatty acid composition for sunflower improvement. The objective of this study was to collect achenes from as many populations of Helianthus verticillatus as possible for the USDA-ARS wild sunflower germplasm collection and to evaluate achenes for oil concentration and fatty acid composition. The exploration covered 1200 miles in the states of Alabama, Georgia, and Tennessee during October, 2003.  Two populations were collected from Georgia and Tennessee with population size varying from 100 to 250 plants. These collections represent the first available populations in the wild sunflower germplasm collection housed at the USDA-ARS North Central Regional Plant Introduction Station, Ames, Iowa. The achene oil concentration averaged 323 g/kg, while the linoleic fatty acid concentration was 749 g/kg, significantly higher than normally observed for populations of wild sunflower growing at southern latitudes. This is the first report of oil concentration and fatty acid composition for this species. Collections of populations of whorled sunflower will assure their preservation in the wild sunflower genebank and their use for future improvement of cultivated sunflower.