HETEROSIS AND COMBINING ABILITY IN SOME COTTON CROSSES IN TWO DIFFERENT ENVIRONMENTS: 1- Yield and yield components traits

Abstract

Two experiments were carried out at Sakha Agriculture Research Station, Cotton Research Institute, Agriculture Research Center, Egypt. The aim of this investigation was to study heterosis and combining ability for the most important traits of cotton (boll weight, seed cotton yield, lint yield, lint percentage, number of bolls per plant and seed index). Eight cotton genotypes 10229 x G.86, G.45, Pima S1, Suven, TNB, CB.58, G. 70 and G. 93 were crossed in half diallel mating design in 2011 season to obtain 28 single crosses. These parents and their respective 28 F1 crosses were evaluated in two planting dates (April and May) in a randomized complete blocks design in 2012 season. The results obtained could be summarized as follows:- 1- Highly significant mean square values were obtained for genotypes, genotypes x dates, parents x dates, crosses x dates for all the studied traits. 2- The best general combiner for most of studied traits was parent (10229 x G. 86). Also the best general combiners for most of studied traits were crosses (10229 x G. 86) x Pima S1, G.45 x G.70, CB.58 x G.70 and CB.58 x G.93 3- The parent (10229 x G. 86) had the best general combining ability for boll weight, seed cotton yield, lint yield and lint percentage under two sowing dates and their combined. 4- The crosses CB.58 x G.93 and G.45 x G.70 showed highly significant desirable specific combining ability for boll weight, seed cotton yield, lint yield and number of bolls per plant at two sowing dates and their combined. 5- Positive heterotic effects relative to the mid-parent were found for most of the traits in the crosses (10229 x G.86) x G.45, G.45 x Suven, G.45 x G.70, TNB x G.70 and C.B 58 x G.93. Also positive heterotic effects relative to the better parent were found for most of the traits in the crosses (10229 x G.86) x TNB, G.45 x Suven and G.45 x G.70 over two planting dates and their combined. 6- Dominance effects were important in the inheritance of boll weight, seed cotton yield and number of bolls per plant traits. The additive gene effects contribute the major portion of gene pool for lint yield, lint percentage and seed index traits. 7- Heritability estimates in narrow sense were low to high for all the studied traits, ranged from 32.17% for seed cotton yield to 91% for boll weight for the combined data. 8- From these results it could be concluded that the crosses CB.58 x G.93 and G.45 x G.70 appeared to be promising for late-planted tolerance therefore could be exploited in breeding program aiming to improve late-planting tolerance.