Abstract:
A diallel set consisting of p2 combinations (p parents ½ P(p-1) F2 hybrids, and the backcrosses among eight rice breeding lines were grown in replicated trails. The eight rice breeding lines were selected from an initial thirty one rice breeding lines comprising eighteen medium maturing rice lines and thirteen early maturing rice lines on the basis of their maturity (early to medium ), plant height (semi – dwarf to intermediate ), tillerring ability (low to high) and spikelet fertility (partly sterile to highly fertile). The diallel study was aimed at elucidating the genetic system underlying the inheritance of quantitative traits; number of days to 50% flowering, plants height number of tillers/plant, number of tillers/m2, number of spikelets/ panicle, number of fertile spikelets/ panicle, 1000-grain weight and grain yield. The results of the diallel analysis show that much of the genetic variation of each of the twelve traits was due to additive effect. Dominance effect was significant in all the traits. Indirect evidence indicated that gene interaction played a negligible role. There was overdominance for number of panicles/m2, number of spikelets /panicles, number of fertile spikelets/panicle and for number of days of maturity. The positive gene effects in the parents were unequally distributed. However, the dominant alleles exceeded the respective alleles for number of fertile spikelets/ panicle and for number of days to maturity and the recessive alleles exceeded the dominant alleles in all the other traits. Heritability estimates were generally high in all the traits for the lines. High percentage co-efficient of variation (c.v %) was observed for parameters such as number of spikelets / panicle. The intercept of the slope was less than zero indicating over dominance for four of the parent while the other parents have partial dominance. The point distribution on the Wr/Vr graph indicates that the differences in parents were genetic in origin. The regression coefficient of the points did not differ significantly this implicating additive gene effects. Significant GCA and SCA effect were observed for most of the parameters. The results indicated that the breeding line (WAB 450 – 1-B 163 – 41) was the best general combiner for most of the characteristics estimated except for days to 50% flowering, number of tiller/ plant, number of tiller/m2, number of days to maturity, number of panicles/hill and number of panicle/m2. A reciprocal recurrent selection method is recommended for further improvement of the selected rice lines especially for grain yield and yield components
