Genetic Mapping and Molecular Characterization of a Broad-spectrum Resistance Gene in Chinese Soybean.

Phytophthora root rot (PRR) causes serious annual soybean yield losses worldwide. The most effective method to prevent PRR involves growing cultivars that possess genes conferring resistance to Phytophthora sojae (Rps). In this study, QTL-sequencing combined with genetic mapping was used to identify in soybean cultivar Xiu94-11 resistance to all isolates tested, exhibiting broad-spectrum PRR resistance. Subsequent analysis revealed was located in the 242-kb genomic region spanning the locus. However, a phylogenetic investigation indicated Xiu94-11 carrying is distantly related to the cultivars containing , implying and have different origins. An examination of candidate genes revealed and share common nonsynonymous SNP and a 144-bp insertion in the sequence encoding a leucine-rich repeat (LRR) region. was considered to be the likely candidate gene of and . Sequence analyses confirmed that the 144-bp insertion caused by an unequal exchange resulted in two additional LRR-encoding fragments in the candidate gene. A marker developed based on the 144-bp insertion was used to analyze the genetic population and germplasm, and proved to be useful for identifying the and alleles. This study implies that the number of LRR units in the LRR domain may be important for PRR resistance in soybean.