DETECTION OF EPISTASIS, ADDITIVE AND DOMINANCE AS GENETIC COMPONENTS FOR SOME COTTON GENOTYPES

This study aimed to determine whether epistasis played a significant role in genetic system for selected traits among several cotton cultivars and to evaluate the importance of additive vs dominance gene effects for traits not influenced by epistasis. The two cultivars referred to as tester L1 and L2 and their F1 (L3) were crossed to each of seven other cultivars. The deviations (cultivars L1 + cultivars L2 – cultivars 2 L3) were analyzed to provide a test of epistasis. Additive- dominance model was fitted to the data for these traits not influenced by gene interaction. The results indicated that total epistasis was significant for lint percentage and upper half mean. The partitioning of the total epistasis, showed insignificance of ( i ) types fixable part of epistasis for all studied traits while the unfixable epistasis, dominance x dominance and dominance x additive was significant only for lint percentage. Additive gene action played the important role for all studied traits except for boll weight. While, dominance effects were insignificant for all traits except for lint percentage. The results indicated difficulty in obtaining clear picture about genetic system of lint percentage and upper half mean. The degree of dominance revealed the predominant nature of additive genetic components. Also the results showed that the dominant alleles were dispersed between testers, as hybrids did not show any proof of directional dominance for all characters