Biometrical Analysis For Gene Action Heterosis And Combining Ability Of Yield And Otheragronomic Traits In Common Bean(phaseolus Vulgaris L.)

Two separate sets of experiments, 4 x 4 complete diallel involving four varieties (Roba-1, Atendaba,rnGobe Rasha and Dimitu) and 6 x 6 half diallel excluding reciprocal crosses using six varieties/genotypesrn(Roba-1, Atendaba, Gobe Rasha, EMP - 236, FEB-147, EAP – 4) hybridized in all possiblerncombinations, were conducted at Bako Agricultural Research Center in 2005/06 main cropping season.rnThe former experiment was carried out to examine the maternal effects while the latter experiment wasrnconducted to identify the major gene action, combining ability (general and specific) and the extent ofrnheterosis (average heterosis and heterobeltosis) in common bean (Phaseolus vugaris L.). In the presentrnstudy, heterosis occurred in varying degrees for different traits studied. This may be due to the jointrnaction of favourable combinations of genes at different loci. Percent heterosis over the mid-parent andrnthe better parent for grain yield ranged from -17.75 to 39.01 % and from -7.97 to 27.16 %, respectively.rn♀Gobe Rasha x ♂EAP-4 and ♀FEB-147 x ♂EAP-4 manifested significant and positive heterosis. Theserncrosses gave 39.01 % and 27.16 % for ♀Gobe Rasha x ♂EAP-4 and 24.98 % and 17.80 % for FEB-147 xrnEAP-4 for heterosis over the mid parent and the better parent, respectively. The heterosis in the formerrnhybrid seemed to be due to genetic diversity observed between the two parents for most of their traits. Onrnthe other hand, ♀FEB-147 x♂ EAP-4 was the only hybrid that showed significant and positive heterosisrnover the mid parent for seed crude protein. Combining ability analysis of 6 x 6 diallel for common beanrnrevealed that general combining ability (GCA) variances were significantly different among parentalrnlines for all the traits studied except number of nodes per main stem, crude protein and grain seed yield.rnThe highest grain yield was 30.95 g per plant in ♀Gobe Rasha x ♂EAP-4, while the least was 20.19 g perrnplant obtained from ♀EAP-4. On the other hand, the highest crude protein content per seed (22.84 %)rnwas recorded by ♀Atendaba x ♂Gobe Rasha while the lowest was obtained by Atendaba x EAP-4 (18.20rn%). Hybrid, ♀Atendaba x ♂EAP-4, also had the lowest organic matter content (95.15 %). Among twentyonerncharacters studied, eleven (days to flowering, days to physiological maturity, plant height, number ofrnseeds per plant, pod length, hundred seed weight, crude protein, anthracnose per leaf, anthracnose perrnpod, angular leaf spot and floury leaf spot) showed significant SCA variances. The significance of bothrnGCA and SCA indicates the importance of both additive and non-additive type of gene actions. However,rnthe ratio of estimate of variance component due to GCA to that of SCA indicates the preponderance ofrnnon-additive type of gene action in the inheritance of the above traits. The result, therefore, suggested thernbreeding methods such as recurrent selection that exploits additive and dominant genetic effects. For therntraits showed non-additive gene action, the suggested strategy would also be an interpopulationalrnbreeding procedure, to exploite the heterosis related to the non-additive gene effects. The F1 crossesrnobtained by the combination of either FEB-147 or EMP-236 produced unique seed color as compared torntheir parents. This may be due to the action of modified gene. The reciprocal effects for all the traitsrnweren’t significant except for seed size, indicating the non-significance of selection for male and femalernparents since maternal effects weren’t evident in these traits and selection based on nuclear genesrninheritance would be effective. However, for seed size, ♀Roba x ♂Gobe Rasha and ♀Gobe Rasha xrn♂Dimitu showed significant and negative reciprocal effects. This effect, therefore, is important as itrndirects the plants breeder in the choice of which parent will be the male or female.rnKey Words/ Phrases: Combining ability, General combining ability, Gene action, Heterosis, Phaseolusrnvulgaris, Specific combining ability

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