Estimation of Components of Variation in Upland Cotton (Gossypium Hirsutum L.) Using Single Tester Analysis

A set of generations of single tester analysis developed from crosses of 17 genetically diverse upland cotton genotypes with tester parent LH 1832, was grown in a randomized complete block design and was evaluated for characters related to yield, fibre quality, earliness and plant type. The tests for epistasis i.e. Ai and Bi revealed the presence of non-allelic interactions for most of the characters studied. The mean squares for additive genetic component was significant for all characters except for number of sympods indicated involvement of additive genetic component for almost all the characters. The mean squares for dominance component indicated the absence of dominance genetic variance for boll setting percentage, boll weight and lint index whereas for all other characters, the contrast for dominance component was significant. The magnitude of additive genetic component was higher for plant height, number of monopods, boll setting percentage, boll weight, seed index, lint index, 2.5% span length and fibre strength. On the contrary, the magnitude of dominance genetic component was higher for number of bolls, seed cotton yield per plant, days to maturity, ginning out-turn, harvest index and fibre fineness where degree of dominance was in the range of over-dominance. The results obtained through this analysis indicated the involvement of additive as well as non-additive genetic components for most of the characters studied and on the basis of these estimates, appropriate breeding method has been discussed for the improvement of these characters.