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Title: COMPREHENSIVE LINKAGE MAP OF BEAN RUST RESISTANCE GENES

Author
item Miklas, Phillip - Phil
item Pastor Corrales, Marcial - Talo
item JUNG, G - UNIV WISCONSIN
item COYNE, D - UNIV NEBRASKA
item KELLY, J - MICHIGAN STATE UNIV
item MCCLEAN, P - N DAKOTA STATE UNIV
item GEPTS, P - UNIV CALIFORNIA, DAVIS

Submitted to: Bean Improvement Cooperative Annual Report
Publication Type: Proceedings
Publication Acceptance Date: 1/1/2002
Publication Date: 4/1/2002
Citation: MIKLAS, P.N., PASTOR CORRALES, M.A., JUNG, G., COYNE, D.P., KELLY, J.D., MCCLEAN, P.E., GEPTS, P. COMPREHENSIVE LINKAGE MAP OF BEAN RUST RESISTANCE GENES. BEAN IMPROVEMENT COOPERATIVE ANNUAL REPORT, 45:125-129. 2002.

Interpretive Summary: Rust is an important disease limiting common bean production across the United States. Genetic resistance is the best control strategy. There are many rust resistance genes available to breeders. The genomic relationship among many of the rust resistance genes is still unknown, however, which precludes efficient utilization of the genes. This study characterizes the linkage relationship among the most important rust resistant genes currently available. Gene tagging and mapping of the genes has revealed better gene deployment and gene pyramiding strategies for development of cultivars with more durable disease resistance. Marker-assisted selection is possible and proposed as a strategy to retain less effective genes in gene pyramids for more durable resistance, and as a means of rapidly deploying effective genes into bean cultivars for the African continent. More durable rust resistant cultivars will save growers millions of dollars by reducing yield loss and dependancy on fungicides.

Technical Abstract: The objective of this study was to co-integrate all the tagged specific rust resistance genes (SR) onto the core map in order to provide a guide or framework from which to determine appropriate allelism tests for characterizing and naming new SR genes. Based on published information and marker work conducted in our laboratory, we were able to map all the genes except the untagged Ur-US#3 and Ur-Resisto genes. There were two primary groups of Middle American genes clustered on linkage groups B4 and B11. These clusters on B4 and B11 indicate that even more complex rust resistance gene blocks, which span even wider genomic regions than previously thought, exist in common bean. The partial map clearly indicates allelism tests necessary for characterizing undefined rust resistance genes. A protocol for naming new bean rust resistance genes based upon the combination of genetic mapping information and allelism testing is forthcoming. The map also indicates linked genes to recombine in coupling for more durable resistance, as conducted recently for the Ur-3 and Ur-11 genes formerly linked in repulsion on B11. Based on current data, recombining Ur-Dorado-108 and Ur-Ouro Negro in coupling (if possible) would provide the broadest level of resistance available at the B4 gene cluster. Studies verifying the utility of the markers for MAS of the linked Ur-genes outside the original mapping populations are generally lacking. Therefore, use of these markers should proceed with caution until their cosegregation with resistance is validated in other populations.