Characterization of resistance to brown stem rot of soybean in five accessions from central China

Brown stem rot (BSR) of soybean [Glycine max (L.) Merr.], caused by Phialophora gregata (Allington & Chamberlain) W. Gams f. sp. sojae Kobayashi, Yamamoto, Negishi, and Ogoshi, can be effectively controlled with genetic resistance. Although three BSR resistance genes have been described, they all map to the same genetic region on linkage group (LG) J. In a previous screening of plant introductions (PIs) for BSR resistance, PI 567296B, PI 567323A, PI 567479, PI 567535B, and PI 567544 from central China were identified as having a high level of resistance. The objective of this study was to determine if resistance in these PIs maps to the same region on LG J where BSR resistance genes were previously identified. To map the resistance genes in these accessions, each PI was crossed to the susceptible cultivar Century 84 and 94 F_2:3 lines were developed from each cross. Lines were evaluated for BSR resistance in the greenhouse and screened with molecular markers from LG J. In all five populations, a quantitative trait locus (QTL) conferring BSR resistance was mapped to the same region on LG J where resistance has already been reported. These results suggest that the BSR resistance genes identified in these five PIs from central China are likely allelic with previously reported BSR resistance genes.