The stem rot (Sclerotium rolfsii) and powdery mildew (Erysiphe polygoni) of bean (Phaseolus vulgaris) are common in the State of Santa Catarina, Brazil. The use of less susceptible varieties can reduce the incidence of these diseases. The main goal of this study was to evaluate the reaction of more than 70 bean genotypes (black and colored groups) to stem rot and powdery mildew. The tests were conducted in a greenhouse in a completely randomized block design. Each seed for the stem rot test was inoculated with two sclerotia of S. rolfsii. For the powdery mildew tests, the plants were naturally infected by air borne conidia. The cultivar Rio Tibagi was used as pattern of median resistance towards stem rot and median susceptibility towards powdery mildew for statistical comparisons. The genotypes less affected by stem rot were (compared to 'Rio Tibagi'): black group - LA 95105428, FT 646, and Access 57; colored group ('Carioca') - BAF 50. The genotype most affected by stem rot was BAF 10. Most of the genotypes did not differ from 'Rio Tibagi' in terms of stem rot intensity. The genotypes most susceptible to stem rot were Access 57 (black) and FGP CF 101 (black). The genotypes less affected by powdery mildew were: black group - Access 60, Access 36, FGP CF 058, TB 95-03, LM95103904, and LP 96-58; colored group - Akitã, LP 94-1, and LP 96-162.
