Submitted to: Journal of Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/23/1997
Publication Date: N/A
Citation: Interpretive Summary: Sunflower is the second most important oilseed in the world, with an annual crop worth billions of dollars. The U. S. National Plant Germplasm System (NPGS) has a special responsibility to conserve genetic materials of sunflower, one of the few crops of worldwide importance that originated, and is genetically most variable, in the continental U. S. The NPGS collection of sunflower genetic material, the most comprehensive in the world, is invaluable for sunflower crop improvement and basic scientific research. Genetic variation in a large sample of wild-growing and cultivated sunflower from the NPGS collection was studied with a newly-refined molecular technique, yielding one of the more extensive databases of genetic information available for any crop. It was found that wild sunflowers from the U. S. Great Plains are genetically more variable than those elsewhere, and were genetically different from wild sunflowers of California and the U. S. Southwest. Wild and cultivated sunflowers were genetically distinguishable, and wild sunflowers from the Great Plains may be the ancestors of cultivated sunflowers. In addition to providing valuable basic scientific information, this research will have the impact of firmly establishing this molecular analysis as a tool for managing invaluable sunflower genetic material more effectively, leading to cost-savings. This research may also make the genetic material easier to use in sunflower breeding, leading to an improved crop that is higher yielding and more resistant to adverse weather and pest infestations.
Technical Abstract: The U. S. National Plant Germplasm System (NPGS) has a special responsibility to conserve germplasm of Helianthus annuus L., sunflower, the second most important oilseed in the world, and one of the few crops of worldwide importance that originated, and is genetically most diverse, in the continental United States. Genetic variation at 20 isozyme loci was surveyed from 146 NPGS accessions of wild and domesticated sunflower via newly optimized starch gel electrophoretic protocols, yielding one of the more extensive data sets of allelic frequencies available for a crop. Standard measures of genetic polymorphism were calculated and a pair wise interaccession distance matrix was analyzed via various numerical taxonomic procedures to assess the efficacy of germplasm maintenance procedures. It was found that wild sunflowers exhibit geographically structured variation, with accessions from the U. S. Great Plains divergent from those originating in California and the U. S. Southwest. In addition, wild sunflowers from the Great Plains included greater allelic diversity than did wild sunflowers elsewhere. Wild and domesticated sunflowers are isozymatically divergent, in large part because of differences in the frequencies of common alleles. Domesticated sunflowers apparently are a monophyletic group, with wild sunflowers from the Great Plains including the most likely progenitor of domesticated sunflowers.