The F2 population developed from the crosses of L-31 x CIM-443 was used to produce Triple Test Cross hybrid population through the cross-combinations from L-31x F2 males, CIM-443x F2 males and F I (L-31x CIM-443) x F2 males. The Triple Test Cross analysis of F1 hybrid population indicated no epistasis or non-allelic interaction for major economic traits of cotton. However, significant epistasis of genotypes was detected for acid value, free fatty acids, and iodine value. Protein contents, wax contents and ash contents or cotton fibre but individually the most or the F2 genotypes computed the significant epistatic values only. For iodine value. Plant height depicted additive and non -additive components of variation. Nodes per plant, sympodia per plant and 10lh sympodial length indicated highly significant differences for additive and non-additive components of variation while non-additive component was positive and highly significant for monopodia per plant. Both the additive and dominant components were highly significant for days to flowering and days to boll opening with complete dominance but incase of first sympodial node, the additive component was significant and non-additive component was highly significant with over dominance type of gene action.
The additive and dominant gene effects were highly significant for seed cotton yield per plant and bolls per plant with partial or incomplete dominance. The boll weight showed partial dominance and the direction of dominance was positive and significant. The lint index indicated over dominance type of gene action. Additive gene effects were more for lint percentage and fibre length. Whereas, the dominant gene effects were of greater magnitude for fibre strength and tibre maturity. The lint percentage, fibre length and fibre fineness indicated incomplete or partial dominance while fibre strength and fibre maturity showed over dominance type of gene action. Additive type of gene effects were greater for cellulose contents with high level of incomplete dominance and the pectin contents also indicated incomplete dominance type of gene action but the dominant gene effects were more for cottonseed oil contents. The cottonseed oil and peroxide value showed over dominance type of gene action.
The correlation studies indicated that monopodia per plant, plant height, sympodia per plant, first pick percentage, fibre maturity, bolls per plant, boll weight, lint index, fibre length, cottonseed oil and cellulose contents of cotton tibre showed positive relationship with seed cotton yield. Whereas, the days to flowering and days to boll opening showed no association with seed cotton yield but fibre strength showed negative correlation with seed cotton yield per plant. Moreover, pectin contents, protein contents, wax contents and ash contents of cotton fibre were negatively associated with seed cotton yield per plant.
The path coefficient analysis revealed that monopodia per plant, sympodia per plant, plant height components, days to flowering, first sympodial node, and bolls per plant, boll weight, first pick percentage, fibre maturity, lint index and cottonseed oil showed direct effects on seed cotton yield. Among the fibre quality traits, fibre fineness only contributed to fibre strength, positively. The specific gravity, acid value, peroxide value and iodine value contributed directly to seed cotton yield per plant. Whereas, pectin contents of cotton fibre depicted positive direct effects with fibre length and fibre fineness.
The maximum positive heterosis of 72.10 percent and 54.63 percent for 10th sympodial length and monopodia per plant was shown by the F1 crosses, C-3 (F1 x F2) and C-12 (L-31 x F2) of the respective cross-combinations. While, among the earliness traits, the maximum positive heterosis of 28.37 percent and 28.95 percent for days to flowering and days to boll opening was depicted by the FI crosses i.e., C-9) (CIM-443 x F2) and C-9) (CIM-443 x F2) of the respective cross-combinations. Whereas, maximum positive heterosis of 34.56 percent for seed cotton yield was given by the F1 cross C-11 from L-31 x F2 cross-combination.
For fibre quality traits maximum positive heterosis of 15.02 percent for fibre strength was shown by the F1 cross (C-8) from CIM-443 x F2 cross-combination. Whereas, the maximum positive heterosis or 50.00 percent and 50.42 percent for acid value and for free fatty acids, respectively, was presented by the F1 crosses i.e C-4 (F1 x F2) and C-4+21 (F1 x F2) cross combinations. While, ash contents or cotton fibre depicted maximum positive heterosis i.e., 72.59 percent in F1 cross (C-I0) of CIM-443 x F2 cross-combination.
Among the morphological traits the nodes per plant showed higher values (95.1 percent) for broad sense heritability along with maximum estimated genetic advance (34.97 percent). The earliness traits i.e. first pick percentage, days to boll opening and days to flowering indicated high values 95.2 percent, 95. I percent ,and 94.3 percent) for broad sense heritability except first sympodial node having 37.1 percent value of broad sense heritability but with maximum estimated genetic advance (85.35 percent of mean). Maximum broad sense heritability values up to 97 percent for seed cotton yield, md its components along with the maximum estimated genetic advance for seed cotton yield i.e., 22.42 percent of mean.
The fibre quality traits revealed high values for broad sense heritability i.e., up to 94.4 percent but fibre fineness showed maximum genetic advance of 9.47 percent. The seed oil contents and its analytical properties also depicted high values up to 99.99 percent for broad sense heritability while cotton fibre chemical constituents depicted maximum broad sense heritability value of 99. 3 percent for wax contents along with 17.76 percent, genetic advance.
The combining ability studies indicated the female parents i.e., L-31 and CIM-443 were found to be the good general combiners for plant height, nodes per plant, l0th sympodial length, sympodia per plant, days to flowering, days to boll opening, seed cotton yield, first pick percentage, lint percentage, fibre length, fibre fineness, seed oil contents, iodine value, protein contents, pectin contents, ash contents and cellulose contents. The third female parent F1 was found to be the good general combiner for specific gravity, free fatty acids, acid value, protein contents and wax contents of cotton fibre.
The crosses of L-3I x F2-15, CIM-443 x F2-I6 and CIM-443 x F2-17 gave positive and significant SCA effects for plant height, nodes per plant and for sympodia per plant were found to be the good specific combiners for improving these traits in the present population through hybridization. Whereas, the crosses i.e., L-31 x F2-1, L-31 x F2-9, L-31 x F2-10, L-31 x F2- 13, L-3I x F2-15, L-3lx F2-18, F1 x F2-6, F. x F2-I6 and F1 x F2-19 showed positive and significant SCA effects for first pick percentage were found to be the good specific combiners for the same. While, crosses of L-31 x F2-1, L-31 x F2-2, L-3I x F2-I1, L-31 x F2-20 CIM-443 x F2-3, CIM-443 x F2-13, CIM-443 x F2-I7 F. x F2-7 and F1 x F2--16 depicted positive and significant SCA effects for seed cotton yield, bolls per plant, boll weight and seeds per boll were found to be good specific combiners for improving the above said traits.
The crosses of L-3I x F2-12, CIM-443 x F2-13 and L-31 x F2-19 indicating significant and positive SCA effects for fibre length, lint percentage and for fibre maturity were found to be good specific combiners for improving these traits. The crosses of L-31 x F2-15, CIM-443 x F2.3, CIM-443 x F2-5, and F1x F2-16 showing significant and positive SCA effects for seed oil contents, free fatty acids, acid value and iodine value were found to be the good specific combiners for the improvement of these traits in the present population. Whereas, the crosses of L-31 x F2-2, CIM-443 x F2-5, CIM-443 x F2-15 and FIx F2 13 with positive and significant SCA effects for fibre chemical constituents were found to be the good specific combiners for improving the above said traits in this population. The F1 populations derived from TTC crosses showed significantly higher percentage of oil contents of 22.60 percent than the female parents (20.40 to 21.30) and F2 males (17.30 to 21.50).Moreover, the 'TTC F1 hybrids depicted higher values for various analytical properties of cottonseed oil than the respective female and male parents. Similarly TTC F1 hybrids indicated better values for various cotton fibre chemical constituents than the respective female and male parents used in the present cross-combinations