HETEROSIS AND SPECIFIC COMBINING ABILITY ESTIMATES FOR ASSESSING POTENTIAL CROSSES TO DEVELOP F1 HYBRIDS IN UPLAND COTTON
Heterosis and combining ability estimates are very useful genetic parameters for identification of potential crosses to develop hybrid cotton. The crosses were attempted in a line x tester mating design, which involved five female and three tester parents, thus 15 F1 hybrids were developed. The experiment was carriedout in a randomized complete block design with four replications. The mean squares due to general combining ability (GCA) of lines and testers and specific combining ability (SCA) of lines x tester interactions were significant. The significance of GCA and SCA variances suggested that both additive and dominant genes were controlling the characters. The high but parallel expression of SCA and heterosis determines the involvement of dominant genes and suitability of F1 crosses for hybrid cotton development. At least five out of fifteen F1 hybrids such as CIM-506 x BH-160, CRIS-134 x BH-160, CIM-496 x Bt-cotton, Sadori x Sindh-1 and Chandi x Bt-cotton manifested higher magnitude of SCA effects for bolls plant-1, boll weight, seed cotton yield and lint%. Almost all the same hybrids demonstrated higher heterobeltiotic effects for bolls plant-1, seed cotton yield plant-1 and lint%. The correlation coefficient between SCA and heterobeltiotic effects further determined the reliability of these two genetic parameters to identify potential F1 hybrids. These correlations between SCA and heterobeltiosis were positive and significant for plant height (r=0.500*), bolls plant-1 (r=0.888**), seed cotton yield plant-1 (r=0.810**), lint% (r=0.550*) and fibre length (r=0.556*). The significant correlations between SCA and heterobeltiotic effects for majority of the traits obviously indicated that both estimates are equally good to predict the potential crosses for hybrid cotton development.