Department of Plant Breeding, P.A.U., Hissar
Genetic divergence, using Mahalanobis's D2-statistic was studied for yield and its components, no. of bolls, boll wt., no. of loculi, no. of sympods, no. of monopods, halo length and ginning percentage, in 33 strains of upland cotton (Gossypium hirsutum L.) evolved from seven diverse crosses.
The varieties differed significantly for the eight characters considered collectively. Amongst the yield components, boll weight contributed the maximum towards the total divergence. The 33 strains were grouped in nine clusters depending on the D2 estimates. Though the clustering pattern of the strains was influenced by their pedigrees, the coherent polygenic and pleiotropic genetic mechanisms reduced the distances between the clusters and the intracluster variances tendcd to be almost parallel, irrespective of the source of origin of the constituent varieties. The directional selection exercised during the evolution of these varieties has resulted in reducing the within and bctween family divergences.
