Genetic divergence study for within boll yield components in Bt germplasm of Gossypium hirsutum L.

Cotton (Gossypium hirsutum L.) is the major fibre crop, which supports economy of Pakistan by adding to foreign exchange earnings and providing employment to the millions of people. The purpose of this study was to assess genetic variability in Bt cotton (Gossypium hirsutum L.) germplasm available in the department of Plant Breeding and Genetics. The data were recorded for seed cotton yield, fibre quality and within boll yield related characters. Analysis of variance showed highly significant difference among genotypes for all the traits. Results of correlation analysis indicated that Seed cotton yield was positively correlated with number of bolls per plant, boll size, seed weight, seeds per boll, seed volume, seed density, lint percentage, lint mass per seed while negatively correlated with fibre quality characters; fibre length, fibre strength and fibre fineness. The data recorded on these traits was analyzed statistically using Principal component analysis. The first principal component was the most diverse component accounted 25.65% variation while PC2, PC3, PC4, PC5 exhibited 20.74%, 15.30%, 14.77% and 9.11% variations, respectively. Out of 12, five PCs exhibited more than 1 Eigen value. Scatter plot showed that genotypes VH-259, VH-282, FH-171, IR-3701, and MNH-886 were not much diverse from each other while genotypes FH-159, CRS-2007, FH-4243, V-15/289 and IR-4 were perceived dissimilar as being apart from each other. Cluster analysis of recorded data, revealed 3 groups and 6 subgroups. Genotypes in group A had highest fibre fineness, genotypes in group B had highest seed cotton yield and genotypes in group C were dominant in fibre strength. Genotypes of group B elucidated maximum diversity against genotypes of group C. Seed volume and seed density showed highest heritability i.e. 99% whilst number of bolls per plant and seed cotton yield showed low heritability i.e. 62% and 64% respectively.