Reaction of common bean genotypes to Sclerotium root rot (Sclerotium rolfsii Sacc.) under screen house conditions in Uganda

Abstract Sclerotium root rot caused by Sclerotium rolfsii Sacc. is one of the major soil-borne diseases of common bean in Uganda and many other countries. An incidence and severity of 100% and 84% respectively, has been reported in the common bean production environments in Uganda. The use of resistant cultivars is reported as the most efficient management strategy against root rot diseases. A few breeding lines showing good levels of resistance have been identified, however currently all released varieties in Uganda lack resistance to the disease. The objectives of this study were to enhance breeding for Sclerotium root rot resistance through validating the resistance in the identified breeding lines and identify new sources. A total of 72 genotypes with two checks (K132 and KWP 9) were evaluated under screen house at NaCRRI (2017A & 2017B) with 9 x10 alpha-lattice design arrangement by three replications. Each genotype was planted in a wooden tray containing pre-sterilized soil inoculated with matured LWE 336-1 Sclerotium isolate. Germination and disease severity were assessed 14 and 28 days after planting (DAP), respectively. The result showed significant (P < 0.001) difference among genotypes both for germination percentage and disease severity, suggesting that substantial genetic variation among the evaluated genotypes. The breeding lines: KWP 12, KWP 17, KWP 9, and ALB 171 were confirmed to be resistance and RRA 41 was identified as a new source of resistance. These genotypes were therefore recommended for further utilization in common bean breeding program to improve Sclerotium root rot resistance in Ugandan susceptible varieties.