Identification And Molecular Markers Of Resistance Gene To Phytophythora Sojae In Soybean

Phytophthora root rot is a devastating disease of soybean in the world. It is caused by the fungus Phytophthora sojae that can survive in soil for a long time, use of resistant cultivars is the most efficient and economic method of controlling the disease, accordingly, identification and utilization resistance genes for P.sojae is very necessary.This study evaluated the resistance of 412 wild soybean species and genotype of soybean cultivars in China. We identified two novel resistance genes from the soybean cultivars WanDoul5 and YouBian30, and constructed the genetic map of these two genes by molecular markers technology. The primary results of this project are as follows.Reactions of 125 soybean cultivars to 10 Phytophthora sojae have been evaluated using in vitro cotyledon inoculation method. Eleven cultivars contained Rps6, eight cultivars contained Rps4, four cultivars contained Rps1, three cultivars contained Rps3, one cultivar contained Rps7, and one cultivar contained Rps2. Among the 125 cultivars evaluated, the cultivars from Anhui and Hubei province had a broader genetic variation in resistance to P.sojae than the cultivars from other provinces.Four hundred and twelve accessions of wild soybean species were,evaluated for resistance to the Phytophthora sojae race PSUSARl from USA by inoculating hypocotyl seedlings. Fifty-six of them were resistant to the "race. Sixty-three accessions exhibited intermediate resistance to the race. Resistance resource from Anhui province was most abundant to this race. Moreover, about 30% of resistant accessions were identified in the accessions from Liaoning, Jiangsu, Hubei, Shanxi, Zhejiang province.Genetic analysis of the F4 progeny derived from the cross between the soybean cultivar YouBian30 and the cultivar XinLiuQing indicated that resistance gene in YouBian 30 is controlled by a single gene. This gene is temporarily named RpsYB30, by Bulked Segregant Analysis (BSA) identified its microsatellite marker that is located in the L linkage group in the soybean genome. This is a novel resistance gene because no resistance gene for phytophthora root rot was reported in the L linkage group.Genetic analysis of the F4 offspring derived from the crosses of the resistant soybean cultivar WanDoul5 with the susceptible cultivars Williams and ZaoShul8, indicated, resistance gene in WanDou to be controlled by a single gene. This gene is temporarily named RpsWD15 and assigned to the D2 linkage group by BSA. This mapping result was confirmed using another mapping population derived from the cross between the WanDon 15 and the susceptible cultivar ZaoShu18.