Browsing by Author "CASTIANO, LEVENE BINAISSA UASSALEIA"

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    STABILITY AND GENETIC ANALYSES OF COMMON BEAN (Phaseolus vulgaris L.) FOR ROOT TRAITS AND SEED YIELD IN MARGINAL ENVIRONMENTS IN CENTRAL MOZAMBIQUE
    (Egerton University, 2024-06) CASTIANO, LEVENE BINAISSA UASSALEIA
    Common bean (Phaseolus vulgaris L.) production is predisposed to extreme weather variability occasioned by effects of climate change. In sub-Saharan Africa, there is limited access to suitable improved varieties adapted to marginal environments. Root system architecture is central to adaptation of common bean to adverse growing conditions and contribute to enhanced yield. Understanding genetic architecture of root traits and seed yield accumulation is a key step towards successful improvement of common bean for adaptation to marginal environments. The objectives of this study, were to: i) determine stability of common bean genotypes for root traits and yield in marginal environments, ii) determine combining ability and estimate genetic correlations of root and agronomic traits iii) determine the root traits associated with water deficit. The study was carried out under field conditions at three locations in Mozambique and in a greenhouse in Kenya. For the field experiments, forty-nine bean genotypes were evaluated in a simple lattice design with two replications for two cropping seasons. Four elite genotypes were selected and crossed to four local cultivars using North Carolina II design. The F2s derived by selfing F1s without selection, were evaluated for adaptability to multi-environments. Residual maximum likelihood estimates revealed significant (P<0.01) genotype-by-environment interaction effects for root traits and seed yield, demonstrating significance of environment on genotypic expression. Acute angles between vectors of different years at the same locations, established repeatability of environments in evaluating genotypes for root traits and yield. Genotype main effect plus genotype-by-environment biplots established stability of genotypes for root traits and seed yield across locations. Genotypes DAB256, DAB398, AFR398 and Guropequeno had superior overall performance and stability for root traits and seed yield across environments. Significant positive correlation between yield and both deep roots and deep root angles and seed yield was recorded. General and specific combining ability mean squares were significant (P<0.05) for all traits measured. General predictability ratios ranged from 0.47 to 0.68 across locations suggested the significance of both additive and non-additive gene action modulating root traits and seed yield. Significant (P<0.05) bivariate and genetic correlations revealed significant association between root traits and yield. Genotypes AFR398 displayed significant positive GCA effects among its crosses for both root and agronomic traits hence was revealed as a potential germplasm for inclusion in a bean yield improvement programme. Moderate to high narrow sense heritability estimates ranging from 0.43 to 0.67 were obtained, signifying likelihood of good response to selection.