Phenotypic and genotypic screening of common bean (Phaseolus vulgaris L.) landraces for resistance to collar rot fungus (Sclerotium rolfsii Sacc.) in North of Iran

Collar rot or southern blight is a serious soil-borne disease in common bean (Phaseolus vulgaris L.) at the North of Iran caused by the fungus Sclerotium rolfsii Sacc. which leads to intense yield reduction in a dwarf bean that is cultivated in Guilan Province. Thirty improved landraces of Guilan dwarf bean were exposed to the infectious disease with the most pathogenic isolate of S. rolfsii, to identify the resistant landraces. Disease Severity Index and some traits were evaluated in greenhouse experiments. Phenotypic screening of the genotypes after scoring and multivariate analysis showed one resistant (Pach-08), 21 tolerant or semi-susceptible and eight completely susceptible genotypes. Also, eight specific SCAR markers linked with resistance to collar rot disease were studied. It was shown that although all SCAR markers were able to identify the resistant genotype (Pach-08), only SMe1Em5 marker could separate susceptible and tolerant genotypes. There were significant relation between the trait “total damage per pot, 21 day” and three SCAR markers (Phs, SAU5, SF6EM3). Overall, indirect selection for resistance to collar rot disease in the Guilan dwarf bean can be achieved through the three SCAR markers.