*Present Address: Institute of Advanced Studies, Meerut University, Meerut, India.
Six populations, namely, P1, P2, F1, F2, B1 and B2 of eight different crosses involving diverse parents, 320 F and AC 138 (local strains) used as females and SA 267 (U.S.A.), 108 F (U.S.S.R.), AG 134 (Pakistan) and 5143 C (Ceylon) used as males, were studied for estimating the nature and magnitude of genetic variance, heritability and degree of heterosis for six characters (G.O.T., seed index, lint index, halo length, fibre maturity and fibre fineness) in upland cotton, Gossypium hirsutum L. The experiment was conducted under two dates of sowing at the University farm Hissar during the year 1968–69.
The character means for the 38 progenies varied under the two dates of sowings. In general, the F1 recorded higher values than the parents and the average values of the segregating generations for the different characters were closer to F1 estimates.
The estimates of the genetic variances and gene-effects showed that all the three types of gene action, namely, additive, dominance and epistasis, were prevalent for all the characters in all the crosses. Amongst the epistatic effects dominance × dominance interaction was maximum followed by additive × additive effects. In many cases the dd interactions were negative and thus had depressing effects on character expression. The complex characters had relatively higher magnitudes of non additive variance as compared to the simpler characters. Under such a genetic structure it was suggested that reciprocal recurrent selection should be followed for most efficient utilization of all the three types of gene effects.
Moderate to very high heritability estimates were obtained for all the six characters. The estimates of expected genetic advance followed the pattern of heritability estimates.
