Combining Ability and Gene Action Analysis for Yield and its Components in Rice (Oryza sativa L.)

Thirty 1 three hybrids generated from crossing three lines with eleven testers were studied along with their parents for combining ability and gene action involved in the expression of characters in rice. The gca and sca effects were significant for all the characters. The magnitude of sca variance was higher than the gca variance for all the characters revealed the presence of predominance of non-additive gene action for all the characters under study. Among parents IR 58025A, RPHR 203-3 and OR 1898-18RAU 720-12-44 were the best general combiners for grain yield and contributing traits. The best combinations for sca effects are IR 58025A/ OR 189818RAU 729-12-44, CRMS 31A/ IR 68830NDR-1-1, IR 58025A/R 304-34, CRMS32A/ R 1130-102-3-88-1 and CRMS 31A/ RPHR 203-3. Promising hybrids based on per se performance, gca and sca effects are IR 58025A/ OR 1898-18RAU 729-12-44, IR 58025A/ R 304-34, CRMS 31A/ RPHR 203-3 and IR 58025A/CHINIKAPOOR. Combining ability analysis helps in the identification of parents with high general combining ability (gca) effects and cross combinations with high – specific combining effects (sca) for commercial exploitation of heterosis and isolation of pure lines among the progenies of the heterotic hybrids. Therefore the present investigation has been conducted to determine the combining ability and gene action for yield and its components using line x tester mating design in rice. Materials and Methods The experimental material comprised of 33 hybrids obtained from the lines involving three newly evolved CMS lines (CRMS 31A, CRMS 32A, IR 58025A) and eleven testers (WAR 120-15-6-2-B-B-3, RPHR 203-3, R 1130-102-3-88-1, IR 68830-NDR-1-1, CR 780-1937, R 1241-18561 *Corresponding author: to2vc@yahoo.co.in 1-1, R 304-34, R 1216-6, CHINIKAPOOR, OR1898-18RAU 729-12-44, WAR 89-4-A9-1-BB-B-2). The set of hybrids were generated in line x tester pattern for the purpose and evaluated along with parents in Randomized Complete Block Design with two replications at Experimental Research Farm under rainfed conditions. Twenty one days old seedlings of hybrids and parents were transplanted in the field. A standard spacing of 20 x 20 cm was adopted for planting and 12 plants were maintained in a single row. Single seeding per hill was transplanted. Recommended package of practices were followed. Observations were recorded on five randomly selected plants in both the replications for thirteen traits viz., Days to 50% flowering, plant height, tillers per plant, productive tillers per plant, panicle length, flag leaf angle, second leaf angle, third leaf angle, leaf area, pollen fertility (%), spikelet fertility (%), harvest index (%) and seed yield per plant. Combining ability analysis was carried out by the method suggested by Kempthorne (1957). Results and Discussion The analysis of variance (ANOVA) showed highly significant differences among lines for most of the characters, except plant height, pollen fertility percentage and harvest index (%). The ANOVA for combining ability of the line x tester set revealed that the variances due to lines as well as testers were significant for characters, indicating significant variation among parents used in this study in terms of general combining ability (Table 1). The significant differences were also recorded for parent’s vs crosses indicating presence of heterosis for these characters. The significance of line x tester for all the characters provided a direct test, indicating that nonadditive variances were important for majority of the characters. The significant mean square of lines and testers indicated prevalence of additive variance for the yield and its components. The magnitude of specific combining ability (sca) variance was higher than the gca variance for all the characters. The comparative variances due