GENETIC VARIABILITY AND ASSOCIATION OF MORPHOAGRONOMIC TRAITS IN SELECTED COMMON BEAN (Phaseolus vulgaris L.) GENOTYPES GROWN UNDER MOISTURE STRESSED ENVIROMENTS IN ETHIOPIA

Abstract

Common beans are grown throughout Ethiopia and an increasingly important commodity in the cropping systems of smallholder producers both for food security and income. However, its production is affected by climate change particularly by intensive drought occurrence. The study of genetic variability under moisture stress areas enables selection of drought tolerant genotypes that would give better yields to ensure food security, especially for poor rural farmers. Therefore, this study was conducted with the objectives of assessing genetic variability among common bean genotypes for seed yield and yield related traits, and to estimate association of traits. A total of 25 common bean genotypes from Melkassa Agricultural Research Center were evaluated for nine yield related traits, at Melkassa and Miesso in 2018. The field experiment was laid out in 5x5 triple lattice design with three replications. The results from combined analysis of variance revealed the presence of significant differences among genotypes for all traits except number of nodes. Moreover, the variation of genotypes for the seed yield per hectare ranged from 770.2 kg to 1399.4 kg with mean yield of 1020.3 kg ha-1. Based on yield advantage gained, the genotypes showed 1.2-59.5% yield advantage over the check. The highest yield advantage was obtained by genotype DRKDDRB-32 followed by DRKDDRB-80. The phenotypic (PCV) and genotypic (GCV) coefficient of variations of the seed yield and yield related traits of common bean genotypes varied in the range between 0.96 to 17.43% and 0.46 to 11.12%, respectively. Heritability in broad sense (H2) and genetic advance as percent of mean (GAM) ranged from 15.42 to 53.39% and 0.5 to 15%., respectively. Although, no high estimated variability components (PCV, H2and GAM), moderate variability components were estimated for internode length, pods per plant, seeds per pod and hundred seed weight. In addition, the values of PCV were moderate for seed yield. In additions, moderate GCV was estimated for internode length and seeds per pod indicating the effectiveness of selection based on the phenotypic performance of the genotypes. The phenotypic correlation coefficient between seed yield per hectare and other traits was positive and significant for days to maturity, grain filling period, pods per plant and seeds per pod and the rest traits like days to flowering, plant height and internode length were not show significant association with seed yield. However, seed yield did not show neither positive nor negative and significant genotypic association with any traits. Among the traits, grain filling period showed positive and highly significant phenotypic correlation with days to maturity. Moreover, positive and highly significant association was showed be between seeds per pod and days to maturity, as well as seeds per pod with grain filling period. On the other hand grain filling period had positive and highly significant genotypic association with days to maturity. Based on the result of path analysis the trait days to maturity, grain filling period, pods per plant and seeds per pod had exerted positive phenotypic direct effects on seed yield. Furthermore, grain filling period, pods per plant and seeds per pod had high positive indirect effect through days to maturity. In addition, pods per plant exerted high positive indirect effect through seeds per pod. Therefore, these traits will have practical importance in selection of common bean genotypes for high seed yield per hectare. Generally, the results suggested the possibility of developing varieties for high seed yield through selection