Identification of sources of resistance to fusarium root rot among selected common bean lines in Uganda

Fusarium root rot (Fusarium solani f.sp. phaseoli) is one of the most important diseases affecting common beans (Phaseolus vulgaris L.). Trials to identify sources of resistance to the pathogen were conducted on 147 bean lines at the National Agricultural Research Laboratories (NARL) at Kawanda in Uganda. The bean lines were from various sources including Uganda, South Africa and the International Centre for Tropical Agriculture in Colombia. A pathogen isolate, FSP-3, was used to produce inoculum for screen house trials through which 46 moderately resistant cultivars were identified. The 46 cultivars were subsequently evaluated in a bean root rot infested field. Data collected included disease severity, colour of hypocotyls, seed size and grain yield, root and shoot weight. Regression analysis showed that field and screen house FRR disease severity data were highly correlated (r= 97%; P?0.01 at 28 DAP data and r=98%; P?0.01 at 56 DAP). Genotypes differed significantly (P=0.05) between 3.2 (MLB-49-89A) and 8.9 (Apac Ongori) in screen house trials and 4.3 (MLB-49-89A) and 8.8 (RWR2075) under field conditions. Fifteen cultivars were moderately resistant at 28 days after planting with four maintaining this reaction at 56 days after planting under field conditions. Disease resistance was highest among cultivars previously selected for resistance to Fusarium wilt and Pythium root rot indicating presence of quantitative trait loci (QTLs) modifying resistance to more than one root pathogen in some lines. Large-seeded varieties and varieties with green hypocotyls tended to be more susceptible indicating genetic correlation between these traits and resistance to Fusarium root rot. Results confirm the presence of sources of resistance which could be utilized in improving resistance in commercial varieties.