Genetic relationships among domesticated and wild sunflowers (Helianthus annuus, Asteraceae)

Abstract

Randomly amplified polymorphic DNA (RAPD) loci were used to investigate the origin and genetic relationships of the domesticated sunflower and its wild relatives. A total of 13 primers was employed for the PCR amplifications, from which 68 polymorphic loci were scored. Analysis of RAPD data supports the origin of the domesticated sunflower from wildH. annuus. The high RAPD identity between wild and domesticatedH. annuus (I = 0.976 to I = 0.997) is concordant with a progenitorderivative relationship. However, the identities are very high and therefore provide little information regarding the geographic origin of the domesticated sunflower. Nonetheless, some inferences concerning relationships among domesticated sunflower accessions can be made. The native American varieties and old landracesform a genetically cohesive group based on RAPD evidence, probably due to their origin prior to the use of interspecific hybridization in the development of sunflower cultivars. In contrast, the modern cultivars are not genetically cohesive, perhaps due to the extensive use of intraspecific and interspecific hybridization in the development of modern sunflower varieties. Likewise, little concordance was observed between the geographical origin and genetic clustering of wild populations—an observation probably best explained by the weedy, human dispersed nature of wildH. annuus populations. The information presented here may be a reliable indicator of genetic relationships among wild and domesticated sunflower accessions. However, the processes generating the observed relationships are complex, and the occurrence of unexpected groupings or absence of predicted ones will probably remain difficult to understand.