USE OF CHLOROPLAST DNA POLYMORPHISMS FOR THE PHYLOGENETIC STUDY OF 7 PHASEOLUS TAXA INCLUDING PHASEOLUS-VULGARIS AND P-COCCINEUS

The genetic variability of seven Phaseolus taxa has been evaluated on the basis of molecular data and the results have used to clarify the p hyletic relationships between several taxa of the P. coccineus L. comp lex. Chloroplast DNA (cpDNA) from 33 populations was digested with six restriction endonucleases, revealing some polymorphisms that made it possible to divide most of the taxa into two main groups: the subspeci es of P. coccineus on the one hand, and P. vulgaris L., P. polyanthus Greenman and P. costaricensis (Freytag and Debouck) on the other hand. P. polyanthus is closer to P. vulgaris than the other taxa of the sec ond group and should be considered as a separate species. The position of the wild species P. costaricensis is intermediate between P. cocci neus and P. polyanthus. P. glabellus shows sufficient polymorphisms at the cpDNA level to be recognized as a separate species, as previously suggested from total seed-protein electrophoretic studies. These resu lts favour the hypothesis of a common phylogeny for P. vulgaris, P. po lyanthus, P. costaricensis and P. coccineus from a single wild ancesto r. Although cpDNA is generally known to be uniform at the intraspecifi c level, some additional polymorphisms were also detected within P. vu lgaris, P. polyanthus and P. coccineus. Further studies are required t o understand the significance of the latter.