CYTOPLASMIC MALE-STERILITY IN SUNFLOWER - ORIGIN, INHERITANCE, AND FREQUENCY IN NATURAL-POPULATIONS

Cytoplasmic male sterility (CMS) in commercial sunflower hybrids is th ought to be derived from a related wild species, Helianthus petiolaris , yet CMS lines are known to carry the chloroplast DNA genotype of H. annuus. To clarify the origin of sunflower CMS, we developed a polymer ase chain reaction-based strategy for detecting CMS in sunflower and s urveyed more than 1,200 plants representing 55 accessions of H. annuus and 26 accessions of H. petiolaris. We also tested 160 progeny from t hree crosses for strict maternal inheritance of organelle DNAs to dete rmine if the apparent discrepancy in the species donor oi the mitochon drial DNA and chloroplast DNA genotypes in CMS lines might result from low-frequency maternal or biparental inheritance of either organelle. No CMS cytotypes were observed in natural populations of either H. an nuus or H. petiolaris, and strict maternal inheritance of organelle DN A was observed. These data provide little insight, therefore, into the origin and population genetics of CMS in natural populations of sunfl ower, except that the evidence for strict maternal inheritance of orga nelles in sunflower makes it unlikely that the mtDNA and cpDNA genotyp es in CMS lines were derived from different species. Nonetheless, the primers developed for assaying organelle DNA variation in sunflower ma y be useful tools for plant breeding programs, cytotype identification , and systematic and evolutionary studies in the domesticated sunflowe r and its relatives.