Genetic diversity and phylogenetic relationships in Vigna Savi germplasm revealed by DNA amplification fingerprinting

The pantropical genus Vigna (Leguminosae) comprises 7 cultivated species that are adapted to a wide range of extreme agroclimatic conditions. Few data are available on the relationships among these cultivated species or on their importance as sources of resistance against biotic and abiotic stresses. Therefore, we optimized DNA amplification fingerprinting (DAF) to estimate the genetic diversity within, and genetic relationships among, a representative core collection of cowpea, as compared with 16 accessions representing cultivars from 6 Vigna species. A set of 26 primers was selected from 262 tested random primers and used for the characterization of 85 Vigna accessions (6 V. angularis, 4 each of V. mungo and V. radiata, 2 V. umbellata, 1 V. aconitifolia, and 68 V. unguiculata), with Phaseolus vulgaris subsp. vulgaris as outgroup. A total of 212 polymorphic bands were used for maximum parsimony analysis. Our results clearly distinguished Brazilian from African V. unguiculata genotypes. At the species level, V. angularis was the most related and V. radiata the most divergent species relative to V. unguiculata. DAF markers were also informative at the intraspecific level, detecting a large diversity between cowpea cultivars. The implications of the presented results for cowpea breeding programs are discussed.