A field experiment was conducted at the Tanzania Agricultural Research Institute (TARI-Selian) to assess the resistance of seventeen improved common bean genotypes against four major foliar diseases: angular leaf spot, bean common mosaic virus, common bacterial blight, and anthracnose. The experiment was laid out in a randomized complete block design (RCBD) with three replications.  Disease ratings were scored using the CIAT 1-9 scale, starting six weeks after planting and repeated every fourteen days for a total of three evaluations. Disease severity scores were then analyzed using GenStat software (version 15). Polymerase chain reaction (PCR) with four specific gene primers was performed to identify disease resistance genes in the bean genotypes. Field trials revealed significant differences (p < 0.001) for disease resistance. The molecular analysis showed that 17.4% of the genotypes possessed all four resistance genes, whereas 7.9% lacked any. There was a weak but statistically significant positive correlation (r = 0.106; p < 0.05) between disease severity scores and the presence of these resistance genes. This suggests that genotypes confirmed to have multiple resistance traits by both methods could be promising candidates for further development and release as new disease-resistant bean varieties for Tanzanian farmers. 

 

Key words: Phaseolus vulgaris L., genotypes, foliar diseases, resistant genes, molecular markers.