Wild Helianthus Species: Collection of a Native Son to Provide a Diverse Germplasm Resource.

The genus Helianthus consists of 51 species and 19 subspecies, with 14 annual and 37 perennial species. The USDA-ARS formally established a wild Helianthus germplasm collection at Bushland, Texas, in 1976. Having the wild species of Helianthus within the boundaries of the USA has facilitated the collection of wild sunflower germplasm. Over 30 explorations in the past 35 years have resulted in the assemblage of a USDA-ARS wild sunflower collection that is the most complete collection in the world.  Presently, it is located at the National Plant Germplasm System Plant Introduction Station at Ames, Iowa and contains 2270 active accessions of which 1388 are annual species accessions and 882 are perennial species accessions. The narrow genetic base of cultivated sunflower has been broadened by the infusion of genes from wild species, which have provided a continued source of beneficial agronomic traits for cultivated sunflower. In a recent survey of 13 major crops for introduced genes from wild ancestors, sunflower ranks fifth with seven traits. The current estimated economic value of their contribution to cultivated sunflower varies from $810 million to $1.1 billion annually. Much of this value is derived from resistance genes for several major diseases including rust, downy mildew, Verticillium wilt, powdery mildew, Phomopsis stem canker, Sclerotinia wilt, charcoal rot, Phoma black stem, and the parasitic weed broomrape. Another substantial contribution of the wild species is the male sterile PET 1  cytoplasm used in most all hybrids worldwide. Significant progress has been made in collecting, evaluating, and preserving the wild Helianthus species germplasm, increasing the available genetic diversity, but thus far only a small portion of the available genetic diversity has been utilized globally for sunflower improvement. This germplasm will be important in the future as a 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.