Molecular Mapping Of Phytophthora Resistance Gene In Soybean Cultivar Zaoshu18

Phytophthora root rot caused by Phytophthora sojae is one of the most important diseases in soybean throughout the world,which can influence the yield.Developoyment of resistant cultivars is the most effective method for controlling this disease.Up to date, 15 Phytophthora resistance genes(Rps gene)have been found,and most of them have been mapped by using molecular markers.Soybean cultivar Zaoshul8 has been identified as an effective source resistant to Phytophthora root rot of soybean.The objectives of this study were to identify and map the Phytophthora resistance gene in Zaoshu18 in order to facilitate its utilization and marker-assisted breeding.Zaoshu18 was crossed with susceptible cultivar Williams to develop mapping populations.The ratio of resistant to susceptible plants in F₂ popuation was 3:1,and The ratio of resistant,seragation and susceptible families in the F₃ lines was 1:2:1,these results indicated the resistance to Phytophthora sojae in Zaoshu18 was controlled by a dominant single gene.The resistance gene was temporarily designated RpsZS18.Zaoshu18 and Williams were crossed and the F₂ seperation population was obtained.753 pairs of SSR primer were screened,and 202 SSR markers were found to have the polymorphism between two parents.The rate of polymorphism of SSR markers was 26.80%.BSA(Bulked segregation analysis) method was used to screen the polymorphic primers.The order of eight co-dominant microsatellite markers linked to RpsZS18 was established as:CSSR45-Satt172-Sat-O69-RpsZS18-Sat-183-Satt274-Sat-198-Sat-415-Sat-289.Based on linkage analysis of SSR markers,RpsZS18 was located on soybean molecular linkage group(MLG) D1b between SSR markers Sat₀69 and Sat₁83 with genetic distances 10.0 cM and 8.3 cM,respectively.This is the first locus for Phytophthora resistance that has been identified on MLG D1b,so it should be novel resistance gene.