|VALENTINI, GISELI - University Of Maringa|
|CREGAN, PERRY - Retired ARS Employee|
|Pastor Corrales, Marcial - Talo|
Submitted to: Bean Improvement Cooperative Annual Report
Publication Type: Trade Journal
Publication Acceptance Date: 7/1/2015
Publication Date: 9/1/2015
Citation: Valentini, G., Cregan, P., Song, Q., Pastor Corrales, M.A. 2015. Interaction between the Ur-4 and Ur-5 bean rust resistance genes. Bean Improvement Cooperative Annual Report. 58:47-48.
Technical Abstract: We aimed to use phenotypic and genetic markers to elucidate the interaction between the Ur-4 and Ur-5 genes for resistance to the rust pathogen of common bean. The resistant reaction of Ur-4 is characterized by necrotic spots (HR) with no sporulation. On the other hand, the resistant reaction of the Ur-5 gene is characterized by tiny pustules (R) less than 0.3 mm in diameter. A total of 182 F2 plants from a Mexico 309 (Ur-5) x Early Gallatin (Ur-4) cross were inoculated with races 40, 44, 53 and 108 of U. appendiculatus. The parents, F1 plants, and 10 check cultivars were also included in this study. Races 53 and 108 were used to detect the presence of Ur-5 and Ur-4, respectively and races 40 and 44 to determine the plausible epistatic interaction between these two genes. In epistatic interactions, the effects of an allele at one gene hide the effects of alleles at another gene. Four SSR DNA markers were also used to corroborate the presence of Ur-4 and Ur-5 in each F2 plant; two markers were linked to Ur-4 and the other two markers were linked to Ur-5. The inoculation of the 182 F2 plants with the races 40 and 44 and the molecular analysis using the SSR markers revealed that the R reaction of Ur-5 was epistatic to the HR reaction of Ur-4 when the two genes were combined. In summary, this study indicates that the Mesoamerican Ur-5 rust resistance gene is epistatic to the Ur-4 Andean gene.