GENETIC-RELATIONSHIPS AMONG DOMESTICATED AND WILD SUNFLOWERS (HELIANTHUS-ANNUUS, ASTERACEAE)

Randomly amplified polymorphic DNA (RAPD) loci were used to investigat e the origin and genetic relationships of the domesticated sunflower a nd its wild relatives. A total of 13 primers was employed for the PCR amplifications, from which 68 polymorphic loci were scored. Analysis o f RAPD data supports the origin of the domesticated sunflower from wil d H. annuus. The high RAPD identity between wild and domesticated H. a nnuus (I = 0.976 to I = 0.997) is concordant with a progenitor-derivat ive relationship. However, the identities are very high and therefore provide little information regarding the geographic origin of the dome sticated sunflower. Nonetheless, some inferences concerning relationsh ips among domesticated sunflower accessions can be made. The native Am erican varieties and aid landraces form a genetically cohesive group b ased on RAPD evidence, probably due to their origin prior to the use o f interspecific hybridization in the development of sunflower cultivar s. In contrast, the modern cultivars are not genetically cohesive perh aps due to the extensive use of intraspecific and interspecific hybrid ization in the development of modern sunflower varieties. Likewise, li ttle concordance was observed between the geographical origin and gene tic clustering of wild populations-an observation probably best explai ned by the weedy, human dispersed nature of wild H. annuus populations . The information presented here may be a reliable indicator of geneti c relationships among wild and domesticated sunflower accessions. Howe ver, the processes generating the observed relationships are complex, and the occurrence of unexpected groupings or absence of predicted one s will probably remain difficult to understand.