Biometrical Analysis For Gene Action, Heterosis and Combining Ability of Yield and OtherAgronomic Traits in Common Bean(Phaseolus vulgaris L.)

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Addis Ababa University


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



Combining Ability, General Combining Ability, Gene Action, Heterosis, Phaseolus Vulgaris, Specific Combining ability