Linkage analysis of soybean Phytophthora root rot resistance loci on chromosome 13
A. GUNADI (1), A. Roberts (1), A. Dorrance (1), S. Berry (1)
(1) Department of Plant Pathology, The Ohio State University, OARDC, Wooster, OH, U.S.A.
Phytopathology 101:S66

Phytophthora root rot, caused by the plant pathogen Phytophthora sojae, is a limiting factor in the production of soybean worldwide. Genes that contributeto the expression of Rps-mediated and partial resistance toward P. sojae provide valuable breeding resources. Rps3 and Rps8 are two distinct soybean loci that mediate hypersensitive-response (HR) resistance against P. sojae. Both resistance genes have been previously mapped within the resistancegene-rich soybean chromosome 13. Rps3 locus is believed to have three known alleles (Rps3-a, Rps3-b, and Rps3-c) each from a different source; PI 86972-1, PI 82.312N, and PI 340046 respectively. Rps8 and each of the Rps3 alleles mediate resistance to different isolates of P. sojae. Two F_2:3 mapping populations were recently generated to elucidate the genetic relationship and segregation pattern between Rps3 alleles and Rps8. The first population originates from a cross between L83-570 (Containing Rps3-a) and PI 399073 (Source of Rps8), and the second originates from a cross between L92-7857 (ContainingRps3-c) and PI 399073. Linkage analysis within chromosome 13 was conducted through combining data from simple-sequence-repeat (SSR) marker polymorphisms, and soybean hypocotyl inoculation tests. Preliminary data from these two populations suggest that this region is segregating for both markers and resistance in a skewed manner, similar to previous studies on these loci.