PHYLOGENETIC-RELATIONSHIPS WITHIN THE GENUS CITRUS (RUTACEAE) AND RELATED GENERA AS REVEALED BY RFLP AND RAPD ANALYSIS

Relationships among 88 accessions representing 45 Citrus species, thre e man-made hybrids, and six related genera were examined for restricti on fragment length polymorphisms (RFLP). Thirty-two Citrus and three M icrocitrus accessions were also examined by random amplified polymorph ic DNA (RAPD) analysis. A measure of relative heterozygosity was estim ated based on;the mean of the number of fragments per individual per p robe-enzyme combination (PEC) divided by total number of fragments per PEC for all non-hybrid Citrus individuals. The presence in a Citrus s pecies of a rare band found also in a related genus was taken as an in dication of possible introgression, while the presence of several frag ments unique to 1 species was used to indicate non-involvement of that species in hybridization events. Most species that have been describe d in the literature as hybrids had high heterozygosity indices and no unique fragments. Distance matrices and dendrograms were generated usi ng simple matching coefficient and neighbor-joining cluster analysis. RFLP and RAPD data gave approximately the same results. These data sho wed C. maxima was affiliated with the papedas C. hongheensis and C. la tipes. C. medica clustered with C. indica when only non-hybrid taxa we re examined, or among limes, lemons, and relatives when all species we re considered. Mandarins did not show strongly supported groupings amo ng themselves, nor with other species. These data showed that, several accessions were probably assigned to the wrong species.