MOLECULAR EVIDENCE AND THE ORIGIN AND DEVELOPMENT OF THE DOMESTICATED SUNFLOWER (HELIANTHUS-ANNUUS, ASTERACEAE)

The domesticated sunflower, Helianthus annuus, is an important economic crop, yet molecular data regarding its evolution are limited. Here we review morphological, geographical, archaeological, and molecular evidence pertaining to its origin and development. New isozyme and chloroplast DNA (cpDNA) evidence is also presented. Morphological, geographical, and archaeological evidence has led to the hypothesis that the domesticated sunflower was derived from a wild/weedy form of H. annuus possibly in the Midwest. Molecular evidence was concordant with this hypothesis. A high degree of enzymatic and cpDNA sequence similarity was observed between wild and domesticated H. annuus, and domesticated H. annuus contained a subset of the alleles and cpDNAs found in wild H. annuus. The extensive polymorphism in the wild plants and the virtual monomorphism in cultivated lines for both isozyme and cpDNA phenotypes further suggest a single origin of the domesticated sunflower from a very limited gene pool. In addition, Native American varieties of the domesticated sunflower were genetically more variable than other cultivated lines, possibly indicating that they gave rise to the other cultivated stocks. Molecular evidence did not, however, allow conclusions as to the exact geographic origin of the domesticated sunflower. © 1990 The New York Botanical Garden, Bronx, NY 10458.