The nature and magnitude of gene effects involved in expression of panicle traits in rainfed rice cultivars were estimated among a wide range of crosses using generation mean analysis. The parental lines comprised of two low-land and six upland rain-fed rice. The lowland parents were used as pollen parents and the upland genotypes were maintained as the seed parents. Crosses were made between them to obtain the F1 hybrids. Backcrosses were produced by crossing the F1 hybrids to their pollen parent to obtain BC1.1 and seed parents to produce BC1.2. The result revealed significant differences (P ≤ 0.05) among the genotypes for all the characters studied. Except for Max x CT7127-49 where P2 and F2 plants of WITA 4 x NERICA 1 that produced long panicles (29.28 and 26.13 cm) that differed significantly (P ≤ 0.05) from other generations, F1 plants produced the longest panicles in the other crosses followed by the F2 plants. For most traits, F1 generation means were higher than the mid-parent values. Significant differences observed between the F1 and F2 generation means in majority of the cases for percentage fertile spikelet and spikelet number per panicle is thought to be due to the diversity in these traits among the parental lines. The means of BCâ‚ and BC2 tended to be located close to those of their respective recurrent parents. Digenic epistatic model was adequate to explain variation in generation means for all the panicle traits for the pooled analysis. Most of the crosses manifested non-allelic interactions for number of spikelet per panicles and fertile spikelet per panicle and is an indication that epistasis is determined to some extent by the genotypes used for the study.
Key words: Generation mean, dominance, additive, epistasis, F1, F2, parental line and backcross.