The Occurrence of Rust Resistance Gene Ur-13 in Common Bean Cultivars and Lines

Summary For the past 10 years, the Andean-type Phaseolus vulgaris cultivar Kranskop has played an important role in South African bean production and breeding. Kranskop shares an ancestor with the internationally important Andean-type rust differential cultivar Redlands Pioneer. The Ur-13 gene in Kranskop and Redlands Pioneer gives protection to numerous internationally reported races of Uromyces appendiculatus and it is imperative to retain this gene in local breeding programmes.In this study, three co-dominant SCAR markers (SE_AACM_ACC430/405, SE_ACAM_CTT310/288 and SE_AAGM_CGT436 Hha I_186/250) were used to trace the origin of Ur-13, and its presence in 71 germplasm accessions, including the international rust differential lines and additional sources of already characterized genes, as well as 78 breeding lines.Each marker was present in approximately 30% of the accessions tested. Only accessions belonging to the Kranskop or Redlands groups contained all three markers. Contrary to expectations, the first two markers, as well as Ur-13, appeared to have originated from a Middle-American-type parent of the Redlands group, California Small White 643, whereas the third marker probably came from the Andean-type cultivar Brown Beauty. This has important implications for the new set of differential lines, as Redlands Pioneer can no longer be regarded as a representative of the Andean gene pool. The markers, in particular SE_AACM_ACC430/405, will be useful in tracing Ur-13 in large seeded breeding material, except where lines such as Mexico 309, PI 181996 and A 286 are used as donors of additional rust resistance genes, as these have the positive alleles of both SE_AACM_ACC430/405 and SE_ACAM_CTT310/288.Part of a Ph.D thesis submitted by the first author to the Department of Plant Sciences, University of the Free State.