“MOLECULAR MAPPING OF THE SOYBEAN STEM CANKER RESISTANCE LOCUS FROM “HUTCHESON”.

CHIESA, M.A.; ORTÍZ, J.P.A.; CAMBURSANO, M.V; PIOLI, R. N. & MORANDI, E.N.

Beijing, China

Conferencia; VIII World Soybean Research Conference VIII (WSRC VIII); 2009

Institute of Crop Science & Chinese Academy of Agriculture Sciences

Soybean Stem Canker (SSC), caused by the fungus Diaporthe phaseolorum var. meridionalis (Dpm), is an important disease in the soybean core region of Argentina. The most successful method for controlling SSC is the use of resistant cultivars. Resistance genes Rdm1 to Rdm4 have been identified by conventional pheno- and genotypic methods. A new resistance gene was identified and characterized pheno- and geno-typically by our group and named Rdm5. Rdm5 and Rdm4 genes are linked in the same linkage group in Hutcheson. The availability of molecular markers linked to Rdm4 and Rdm5 genes will improve molecular-based screens for SSC resistance. Our approach to mapping these two Rdm genes involved crossing the resistant cultivar Hutcheson (Rdm4 and Rdm5) with the highly susceptible breeding line J77-339 to create two F2 segregant mapping populations: J04b and J04c. These populations were screened for SSC phenotypic reaction in progeny tests in the F2:3 generation using two previously characterized local isolates of Dpm. Bulked segregant analysis with AFLP markers was performed on DNA samples from members of the J04b population and polymorphic SSR markers, uniformly distributed in the soybean genome, were analyzed in both populations. By using the complete segregation information from both populations and the mapping programme JoinMap ver. 1.4 the region that contained the Rdm4 and Rdm5 resistance genes was localized in the molecular linkage group A2 of the integrated soybean linkage map. In MLG-A2 there are other genes that conferred resistance to pathogen organisms like bacteria, fungus and nematodes.