Assessment of genetic diversity in cowpea (Vigna unguiculata)

Sixty six genotypes of cowpea (Vigna unguiculata (L.) Walp) were investigated to understand the extent of genetic diversity through twelve quantitative traits. Mahalanobis’s D2 analysis established the presence of wide genetic diversity among these genotypes by the formation of 23 clusters. Cluster I had the maximum number of genotypes i.e 22 and cluster 23 had only one genotype. Intra cluster distance analysis revealed that the minimum intra cluster distance was observed in the cluster II. The inter-cluster distance (D) was found to be the maximum between the clusters XXII and XXIII and the same was minimum between clusters II and V. The results indicated that grain yield per plant contributed maximum to the total divergence followed by 100 seed weight and days to 50% flowering. Number of branches per plant had least contribution to the total divergence followed by petiole length. The existence of wide genetic diversity among the types chosen from the same geographical location was obviously seen. In the present study, the variety Vellayani local had the maximum value for plant height and pod length and thereby distinguished from other varieties and it is present singly in the cluster XXIII. Hence it is proved to be widely divergent, since its yield is high, it can be used for further crossing and yield improvement. The cluster XVIII had the highest cluster mean values for number of clusters per plant and the cluster XIV has the highest mean value for grain yield per plant. These two clusters may be utilized in crossing programme which may yield in a wide spectrum of variability and for selection for seed yield in the subsequent generations. The clustering pattern of the varieties in the present study clearly indicated that there was no parallelism between genetic and geographic diversities. Based on the mean performance and genetic divergence, the genotypes Vellayani local, NBC 7, Lola, CP 18, CP 150, ACM 05-07 can be used for crossing and further selection.