Identification of quantitative trait loci conferring partial resistance to Phytophthora sojae in soybean PI 427106
S. LEE (1), M. Mian (2), H. Wang (3), L. McHale (4), C. Sneller (1), A. Dorrance (3)
(1) Department of Horticulture and Crop Science, The Ohio State University, Wooster, OH, U.S.A.; (2) Corn and Soybean Unit, USDA-ARS, Wooster, OH, U.S.A.; (3) Department of Plant Pathology, The Ohio State University, Wooster, OH, U.S.A.; (4) Department of Horticulture and Crop Science, The Ohio State University, Columbus, OH, U.S.A.
Phytopathology 101:S100

Phytophthora root and stem rot caused by Phytophthora sojae is a destructive disease that limits soybean yield around the world. Fifteen resistance genes (Rps) to P. sojae have been identified, but adaptation by the pathogen has made many of these R-genes ineffective. In addition to Rps-gene resistance, partial resistance controlled by quantitative trait loci (QTL) provides effective long-term defense against many pathotypes. The objective of this study was to identify QTL conferring partial resistance against P. sojae from a new genetic source, PI 427106. Ninety-four recombinant inbred lines (RIL) from a F_6:8 population of OX20-8 (susceptible) by PI 427106 (with high level of partial resistance) were used in this study. The population was genotyped with approximately 200 SNPs using BeadXpress system and the genetic map was constructed. To evaluate the level of partial resistance, 7-day-old seedlings (10 plants per RIL) were inoculated on the root with P. sojae isolate 13.S.1.2 and lesion length was measured 7 dai. The mean lesion length of ten seedlings was statistically analyzed to obtain the best linear unbiased predictor (BLUP). Using marker genotypes and BLUP values composite interval mapping located three QTL on chromosome 13, 16, and 18, which explained 4.9 ~ 16.5% of the phenotypic variation, respectively. These results suggest that this soybean accession may be an important source of partial resistance in developing germplasm for breeding new cultivars with more durable resistance to P. sojae.