Abstract

Common bean (Phaseolus vulgaris L.) is grown in regions where water deficit during reproductive development significantly reduces yield. The objective of this study was to assess morpho-physiological response to post-flowering drought stress in small red seeded common bean genotypes of diverse origin under field conditions. Forty-nine genotypes were evaluated in a 7 x 7 simple lattice design under two soil moisture regimes, non-stress (NS) and drought stress (DS) growth conditions in Gofa, Southern Ethiopia. Drought stress was initiated at flowering stage by withholding application of irrigation water. Significant differences were found among genotypes and between the soil moisture regimes except for days to flowering for the morpho-physiological traits considered. Drought stress reduced seed yield, harvest index (HI), seed per pod, seed per plant and 100-seed weight by 59%, 39%, 15%, 29% and 19%, respectively. Drought-induced reduction in seed yield of the tested genotypes ranged from 9% in ECAB-0427 to 89% in REDWOLAITA. With the highest yield of 1365.7 kg ha-1 under drought stress, ECAB-0427 was the most drought tolerant genotypes, whereas with the lowest yield of 111.9 kg ha-1, REDWOLAITA was the most sensitive genotype to the stress imposed. Superior performance of ECAB-0427 under drought stress was attributed to the maintenance of higher leaf area index (LAI) (2.8) and pod harvest index (PHI) (67.6) compared with a LAI and PHI of 0.8 and 22.1, respectively, for REDWOLAITA. Yield under drought stress was correlated with yield under non-stress (r = 0.68, p<0.01) implying that selection under drought conditions may lead to the identification of genotypes suitable for optimal conditions. Significantly higher correlation detected between GM (geometric mean) and seed yield under drought stress (r = 0.95, p<0.01) entail that the drought index can be used as one of the most important selection criteria in identifying drought resistant small red bean genotypes.

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