A quantitative trait locus influencing tolerance to Phytophthora root rot in the soybean cultivar 'Conrad'

'CyConrad', a soybean cultivar tolerant to Phytophthora root rot (PRR), and 'CyOX760-6-1', a breeding line with low tolerance to PRR, were crossed. F-2 derived recombinant inbred lines were advanced to F-6 to generate a population through single-seed descent. This population was used to identify quantitative trait loci (QTLs) influencing PRR tolerance in 'CyConrad'. A total of 99 simple sequence repeat (SSR), or microsatellite, markers that were polymorphic and clearly segregated in the F-6 mapping population were used for QTL detection. Based on the data of PRR in the field at two planting locations, Woodslee and Weaver, for the years 2000 and 2001, one putative QTL, designated as Qsatt414-596, was detected using MapMaker/QTL. Qsatt414-596 was flanked by two SSR markers from the linkage group MLG J, Satt414 and Satt596. Satt414 and Satt596 were also detected to be significantly (P < 0.005) associated with PRR using the SAS GLM procedure and were estimated to explain 13.7% and 21.5% of the total phenotypic variance, respectively.