Information on the response of basic generations of a population to drought stress may help in designing effective breeding procedure and identification of selection criteria that can be used to develop suitable cultivars. This study was carried out to ass differential effects of drought stress initiated at flowering stage on the growth, physiological and yield related traits of six basic generations of two common bean populations made of crosses between pairs of drought resistant and susceptible par Melka-Dima X SAB623). On average, the stress imposed reduced the various characters examined in the range of 3% (pod length) to 28% (seed yield). Canopy temperature and chlorophyll content, however, increased in response to the stres two populations were compared, those obtained from Melka sensitive to drought than Roba 1 X SERsusceptible parents (Roba 1 and Melka-Dima) had the highest dr in growth, stomatal conductance and all yield related traits whereas P1, F1 and BC1 exhibited better performance under drought stress for the different characters studied. Under drought, F1 generation produced higher seed yield than indicating the presence hetrosis under the stress condition. With geometric means of 3722 and 4077, F1 and P1 were found to be the most drought resistant generations in Roba 1 X SER-16 and Melka-Dima X SAB-623 crosses, respectively drought stress of these generations was associated with the maintenance of higher stomatal conductance, leaf area and aboveground biomass as well as greater ability to remobilize biomass to reproductive sinks (pods and seeds).

Information on the availability of genetic variability and mode of gene action are critically important for choosing effective breeding methods that result in appreciable improvement in performance under drought stress. The objectives of this study were to estimate the gene action for drought resistance of quantitative traits and also to estimate the components of variance and heritability of drought resistance in common bean. Field experiment was carried out using six generations of two populations made of crosses between pairs of drought resistant and susceptible genotypes (Roba-1 × SER-16; Melka-Dima × SAB623). The treatments were laid in a split plot design with three replications, where watering regime was assigned to the main plot and generations to the sub-plot. Drought stress was initiated at flowering stage by withholding application of irrigation water. Scaling test and generation mean analysis brought out that individual crosses greatly differed for the gene action and on an overall basis all the types of gene action, additive, dominance and epistasis were important for drought resistance in common bean. Both additive and non-additive types of gene action were important in governing the inheritance of the traits considered. However, additive types of gene actions were important in the inheritance of number of pod per plant in Roba-1 × SER-16 and above ground biomass in Melka-Dima × SAB-623 under drought stress. Medium to high broad and narrow sense heritability were found for most of the traits under both watering regimes. Evidences have unfolded that chances to find stress tolerant breeding material in segregating populations of the two crosses were promising. The presence of significant amount of all types of gene action for the important traits imply that methods which can utilize all of them such as recurrent selection and multiple cross could be employed in breeding beans for drought environments.