Characterization and screening of Malawian common bean ( <i>Phaseolus vulgaris</i> L.) germplasm for drought tolerance and breeding potential

Abstract The common bean ( Phaseolus vulgaris L.) is a key food and nutritional crop in Sub-Saharan Africa, where recurrent drought severely limits its productivity. Identifying common bean accession lines that are drought-adapted and suitable for crop breeding programs is therefore imperative. In this study, 270 common bean lines were first screened for tolerance to low soil phosphorus, from which 30 lines were selected and further evaluated under drought conditions to identify germplasm with combined tolerance to nutrient and water stress. Substantial variation among genotypes was observed in biomass production, shoot-to-root ratio and drought response indices. Two lines, Kha 30 and Kha 76, were identified as tolerant to both low soil phosphorus and drought, consistently outperforming the drought-sensitive line Chuma in growth rate, relative water content, membrane stability and root ion accumulation. Traits associated with drought tolerance, including reduced specific leaf area and enhanced micro-nutrient accumulation, further support the value of these accessions as genetic resources for pre-breeding. These findings suggest that Kha 30 and Kha 76 are important drought-resistant genetic resources with considerable potential to strengthen common bean improvement programs in Malawi and similar drought-prone agro-ecological areas in Sub-Saharan Africa.