Assessment of genetic diversity based on principal component analysis in vegetable cowpea (Vigna unguiculata (L.) Walp.) germplasm

Data on key flowering, maturity and yield attributes of 87 cowpea accessions including exotic and indigenous accessions were subjected to genotype clustering and principal component analysis (PCA) to identify diverse elite accessions for vegetable purpose. Based on PCA, PC-I, PC-II and PC-III had eigen values more than one, which contributed to 90.87% of total cumulative variability among germplasm. PC-I followed by PC-II and PC-III contributed maximum (46.34%, 28.40% and 15.63%) towards variability. The PC-I exhibited factor loadings in the positive sign for days taken to the happening of first flowering, days required to 50% of plants to flower, days taken to setting of first fruit and days to first harvest, while, except pods per plant and per plant pod yield, all other factors registered were positive towards PC-II. As many as nine traits have contributed positive factor loadings towards PC-III. Cluster analysis grouped 87 vegetable cowpea genotypes into 16 divergent clusters, cluster-II comprised a maximum of 45 genotypes followed by cluster I and XII. As many as 10 out of 16 clusters were solitary with unique genotypes revealing a greater amount of diversity among the germplasm. As confirmed by the D-2 statistic, the maximum diversity was elucidated by the VI cluster genotypes against those of cluster-XVI and between clusters VII and XVI as well. The maximum uniformity was observed between cluster-IV and cluster-V. Selection of genotypes should be based on the pods formed per plant followed by days taken to 50% flowering of plants, as their contribution for the total divergence of the germplasm was the maximum. Therefore, the investigation suggests that cross combinations between divergent accessions of cluster-V, III, and II, may lead to maximum heterosis in realizing hybrid breeding and isolation of superior breeding lines as well in vegetable cowpea breeding.