Genetic diversity in a colombian bean (phaseolus vulgaris l.) collection as assessed by phaseolin patterns and isoenzymatic markers

Abstract

The knowledge of genetic diversity patterns increase the efficiency of the conservation and the enrichment of the genetic resourses. This study allowed the discrimination of the existing genetic variability in a Colombian collection of shrub bean by phaseolin patterns and isoenzymatic markers. Bean seed proteins revelated that the phaseolin patterns types T and C are predominant in the Andean pool, type S in the Meso-American pool and type B in Colombian and Central American accessions, with a predominance of 81% of phaseolin T in the Andean pool, and 78% of phaseolin B in the Meso-American pool. The accessions of cultivated and wild beans showed variation in 10 of the studied enzymatic systems: ab-EST, GOT, ab-ACP, DIA, PRX, ASD, 6-PGDH, MDH, IDH and ME; and monomorphism in the PGI and PGM systems. The isozyme systems presented 19 bands of activity, of which 74% were polymorphic loci. Both in the Andean and Meso-American genetic pools, the loci Mdh-1, Mdh-2, b-Est-1, Skdh and Me exhibited polymorphisms. Single alleles in the Meso-American pool were found in 6-Pgdh-2103, Mdh-1100, Idh100, a-Est-1100, a-Est-2100, and Dia-195; and in the Andean pool, in 6-Pgdh-1100, and Acp-2100. For degree of domestication, the wild and cultivated accessions presented polymorphisms in 58 and 47% of the loci, respectively. The enzymatic relationship cluster analysis of the studied bean collection revealed three distinct groups of accessions; namely the Meso-American pool, including its cultivated and wild accessions; the Andean pool, which is mainly comprised of cultivated accessions, plus the wild DGD-626; and finally, featured by a high degree of enzymatic polymorphism and by the presence of the type I phaseolin, a third group that contains only a wild accession from the northern, Peruvian Andes.