Allelism Tests between the Rust Resistance Gene Present in Common Bean Cultivar Ouro Negro and Genes Ur-5 and Ur-11

The pathogenic variability of the fungus Uromyces appendiculatus is an obstacle for the creation of rustresistant common bean (Phaseolus vulgaris L.) varieties. Gene pyramiding is an alternative strategy for the development of varieties with durable resistance. However, to reach this goal it is important to identify different genes with ample resistance spectra. Cultivars Ouro Negro, Mexico 309 and Belmidak RR-3 have been shown to be resistant to several rust races identified in the state of Minas Gerais, Brazil. Ouro Negro is the only rust resistance source being used in the BIOAGRO/Universidade Federal de Vic¸osa (UFV) breeding programme, which aims at pyramiding resistance genes in the carioca-type cultivar Ruda´ . It would be also interesting to use Mexico 309 (Ur-5) and Belmidak RR-3 (Ur-11) in the breeding programme. However, there is no available information on the possible allelic relationships between the Ouro Negro resistance gene and Ur-5 and Ur-11. This work aimed at: (1) determining the allelic relationship between the Ouro Negro resistance gene and Ur-5 and Ur-11; and (2) evaluating a random amplified polymorphic DNA (RAPD) marker previously reported as being linked to Ur-11, in populations from crosses between Belmidak RR-3 and Ruda´ . The allelism tests confirmed that the Ouro Negro rust resistance gene is distinct from Ur-5 and Ur-11 and the molecular analyses confirmed that the RAPD marker can be used in our breeding programme to develop carioca-type cultivars with the Ur-11 gene.