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The analysis of variance for combining ability for line x tester design revealed highly significant difference among the crosses for all the traits except L:B ratio. Mean squares due to lines in respect of gca were significant for spikelets per panicle, filled spikelet per panicle and plant height. Variances due to line x testers, representing sca were found highly significant for spikelets per panicle, filled spikelet per panicle and days to 50% flowering. In line x tester analysis the estimates of σ2 gca were higher than σ2 sca for all 13 characters which suggested predominance of additive gene action. On the basis of gca effects, IR 63731-1-1-3-3-2, IR 2-9-B-1-5 and CSRS(C-52-1-1) were identified as most promising parents for involving in hybridization programme for obtaining desirable segregates for grain yield and other characters.A single cross, IR 2-9-B-1-5/F1 showed significant and positive sca for grain yield per plant along with significant and desirable sca effects. This cross may be exploited for isolating desirable segregants in segregating generation.
Keywords: Combining Ability, Gene Action, and Yield.