Fifty years of collecting wild Helianthus species for cultivated sunflower improvement

Abstract Wild Helianthus species have been undeniably beneficial in sustaining the sunflower crop by providing plant breeders with a diverse genetic pool of potentially useful traits. Exploration to collect populations of wild sunflowers is one of the more difficult and challenging activities in the conservation and utilization of these valuable genetic resources. The logistics of collecting requires careful planning, locating the target species, obtaining permission to access and collect, and timing the exploration to ensure the availability of mature seed. The US Department of Agriculture, Agricultural Research Service (USDA-ARS) established the wild Helianthus seed collection in 1976 at Bushland, Texas with the goal of collecting and conserving the broadest representative genetic diversity possible and serving as a central repository of germplasm and related information. In 1985 this collection was transferred to UDSA-ARS, North Central Regional Plant Introduction Station, Ames, Iowa. Over the last half century, 37 explorations were undertaken covering 175,000 km to collect the 53 Helianthus species from their distributional ranges in the forty-eight conterminous states in the US, three Canadian Providences (Manitoba, Saskatchewan, and Alberta), Argentina and Australia. The many explorations have created a global crop wild relatives (CWR) genebank collection. The current wild CWR sunflower genebank contains 2562 accessions of 53 species with 1065 wild Helianthus annuus accessions (42 %), 617 accessions representing populations of the 13 other wild annual species (24 %), and 880 accessions representing 39 perennial species (34 %). This collection is the largest and most genetically diverse ex situ sunflower collection in the world and is vital to the conservation of wild sunflower species for the global sunflower community.