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item MIENIE, C.M.S.
item Miklas, Phillip - Phil

Submitted to: Journal of Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/2/2004
Publication Date: 4/5/2005
Citation: Mienie, C., Liebenberg, M.M., Pretorius, Z.A., Miklas, P.N. 2005. Scar markers linked to the phaseolus vulgaris rust resistance gene ur-13*. Journal of Theoretical and Applied Genetics. 111:972-979.

Interpretive Summary: Bean rust is a serious disease of dry bean (pinto, kidney, black) and snap (garden) beans worldwide. The fungal pathogen is highly variable and difficult to control with fungicides. Genetic resistance is highly useful for controlling this disease but can be short lived due to the pathogen's ability to overcome individual resistance genes. Therefore, breeders combine resistance genes to make it harder for the pathogen to overcome resistance. Thus, pyramided rust resistance genes provide for a more durable long-lasting resistance. In this work, USDA-ARS collaborated with pathologists from South Africa to identify a new resistance gene Ur-13 that is highly effective against rust pathotypes that prevail in the African Continent. Ur-13 pyramided with other genes will provide a more durable and broad based resistance to bean rust in bean cultivars grown in Africa. This work highlights the involvement and contribution of USDA-ARS to international agriculture.

Technical Abstract: Rust in common bean is caused by Uromyces appendiculatus which exhibits a high level of pathogenic diversity. Resistance to this disease is conditioned by a considerable number of genes. Pyramiding of multiple resistance genes is desirable and could be simplified by the use of molecular markers closely linked to the genes. The resistance gene Ur-13, present the South African large seeded cultivar Kranskop has been used extensively in the local breeding program. The purpose of this study was the development of a molecular marker linked to Ur-13. An F2 population derived from a cross between Kranskop and a susceptible cultivar Bonus (SA) was used in combination with bulked segregant analysis utilizing the amplified fragment length polymorphism (AFLP) technique. Several AFLP fragments linked significantly to the rust resistance and five were successfully converted to sequence characterized amplified region (SCAR) markers. The co-dominant SCAR marker derived from a 405 bp EAACMACC fragment, KB126, explained 91% of the variation in phenotype and was located 1.6 cM from the gene. Two additional SCAR markers and one cleaved amplified polymorphic sequence (CAPS) marker were located further from the gene. The CAPS marker flanked the gene and was located 14.7 cM from Ur-13. The gene was mapped to Linkage Group B8 of the Davis core bean map.