RELATIONSHIPS OF VIGNA-UNGUICULATA (L) WALP, V-VEXILLATA (L) A-RICH AND SPECIES OF SECTION VIGNA BASED ON ISOZYME VARIATION

Isozyme variation in 25 accessions of wild and cultivated Vigna unguic ulata, 49 accessions of seven wild species belonging to section Vigna, and 11 accessions of V. vexillata (subgenus Plectrotropis) was scored at 17 putative loci to assess genetic relationships within and among species. The wild species selected for this study are among those whic h carry important agronomical traits useful in cowpea (V. unguiculata) breeding programs. Allelic frequencies were calculated and Nei's gene tic distances were obtained. Low levels of intraspecific variation wer e observed for V. heterophylla, V. luteola and V. racemosa, whereas th e other species showed a higher polymorphism. Vigna unguiculata posses sed intraspecific genetic distances comparable to those previously fou nd by other authors. Most of the isozyme variation was apportioned amo ng species. Although V. luteola and V. marina had an interspecific gen etic distance resembling the range observed at intraspecific level, al l the other species showed very high interspecific distances. Vigna un guiculata was relatively closer genetically to V. vexillata than to th e species belonging to section Vigna.