Principal component analysis and determination of the selection criteria in fodder cowpea (Vigna unguiculata (L) Walp.) genotypes

A critical examination of the genetic variability helps to make good decisions in a crossing programme. The present investigation consisted of thirty diverse germplasm lines of cowpea (Vigna unguiculata (L) Walp.) in which divergence was studied. On the basis of relative magnitude of cluster distances, all the 30 genotypes of cowpea were grouped into five major clusters. Cluster pattern revealed that cluster II was the largest group consisting of 17 genotypes followed by cluster III (6 genotypes) and cluster I (5 genotypes). Cluster IV and V each had only one genotype where each genotype within a cluster was closest to the cluster mean. The highest intra-cluster distance was observed for cluster II followed by cluster I, cluster III and cluster IV and V. Cluster I had highest mean for dry matter, dry matter per day, plant height and number of branches per plant. Cluster II had highest mean value for leaf length. Similarly cluster III showed highest leaf breadth. Green fodder yield, green fodder per day, days to 50% flowering, leaf weight and straw weight showed highest cluster mean in Cluster IV. The first principal component explained 32.1% of the total variation. The second, third, fourth and fifth principal components explained 17.1, 16.1, 13.6 and 11.7% of the total variance, respectively. It was clear that the first factor expressing the combined effect of stem and leaf weight on green fodder yield can be regarded as green fodder yield factor. PF-2 was associated with dry matter characters, hence can be considered as dry matter yield factor. Similarly PF-3, PF-4 and PF-5 can be regarded as yield contributing factors collectively.