ISOZYMIC DIVERSITY IN BLACK DRY BEAN NATIVE POPULATIONS

Abstract

Genetic diversity in 50 landraces of black-bean (Phaseolus vulgaris L.) from different geographic regions of México, was isozymically assessed on 20 different isozymes. Isozymic extracts were obtained by grinding radicules from five seedlings. Six isozymes showed polymorphism: Shikimic acid dehydrogenase (SAD) with two loci; Diaphorase (DIA) with five loci; Malic enzyme (ME) with two loci; Estearease (EST) with two loci; Phosphohexase isomerase (PHI) with three loci, and Malate dehydrogenase (MDH) with two loci. Eleven
loci out of 16 were polymorphic (68.7 % of polymorphism). Polymorphism per locus was from one to six alleles, with a mean of three alleles per locus. Cluster analysis, based on Nei’s genetic distances according to the mean linkage method (UPGMA), showed the largest genetic diversity in populations from the central zone and from the tropics of México. A distribution pattern based on specific alleles was established; and within each group a continuous distribution of diversity was observed. Isozyme analysis was useful to show the amplitude in the distribution of the genetic diversity among black bean Mexican landraces, as well as its usefulness for characterization of genetic diversity in this species.