Common Bean Improvement

Fusarium root rot (FRR) is an important soil-borne disease of common bean worldwide. In Africa, minimal or no control measures are applied resulting in heavy yield losses. Popular varieties are susceptible and resistant ones have undesirable traits. Four isolates were tested for pathogenicity and one, FSP-3, subsequently utilised in screening trails to identify resistant varieties. Two soil compositions, i) 50% swamp soil:50% forest soil composition and ii) forest soil, and two irrigation schedules i) once a week and ii) daily, categorized varieties most distinctly according to their reaction to FRR. 147 common bean varieties were evaluated in a screenhouse and 46 of these in the field. Nine varieties were selected as sources of resistance. Evaluation of 66 F1 and F2 populations plus reciprocals showed that FRR resistance was mainly governed by additive genes with a few crosses displaying significant SCA effects. Significant maternal effects and non-maternal were observed. Number of resistance genes varied from 2-9, allelism test suggested presence of many loci governing this trait. Heritability (H) varied from 0.22-0.69 and h2 was estimated at 0.35-0.49.