Inheritance of resistance to Uromyces appendiculatus in the South African dry bean cultivar Kranskop

Abstract

The inheritance of resistance to race RSA-Ua7 of the rust pathogen Uromyces appendiculatus in the South African dry bean (Phaseolus vulgaris) cultivar Kranskop, as well as the relationship of rust resistance between Kranskop and the international rust differential cultivars Redlands Pioneer and PC-50, were determined. Segregation of progeny from a Bonus x Kranskop cross, and the backcross to Bonus, indicated that rust resistance in Kranskop is conditioned by a single dominant gene. It is proposed that this gene be named Ur-13, according to standard protocol. No segregation occurred in the F₁ and F₂ plants of a Redlands Pioneer x Kranskop cross and its reciprocal, implying that resistance to race RSA-Ua7 is conditioned by the same gene in Kranskop and Redlands Pioneer. Segregation of progeny from both the PC-50 x Kranskop and Kranskop x PC-50 crosses indicated the presence of two independent genes, with an additive effect to race RSA-Ua7.