QTL Mapping of Resistance Genes to Powdery Mildew in Cucumber(Cucumis sativus L.)

【Objective】 The cucumber inbred line K8 with high resistance to powdery mildew was used as materials to study.the inheritance of resistance gene to powdery mildew in K8 and to conduct QTL mapping for these genes so as to provide a theoretical basis for the resistance mechanism and molecular assistant selection(MAS) breeding.【Method】 An artificial inoculation method was adopted to test the degree of resistance to Podosphaera xanthii(syn.Sphaerotheca fuliginea) for the F2:3 family lines derived from the cross of K8×K18(susceptible lines).SSR analysis,combined with bulked segregation analysis(BSA),was done on the DNA of F2 and F2:3 population using 2 360 pairs of SSR primers.JoinMap 4.0 and MapInspect software were used to construct SSR linkages and to make sure the corresponding relations between these SSR linkages and cucumber chromosome.QTL analysis on powdery mildew resistance genes was conducted by MapQTL4.0 software.【Result】 The inheritance of the resistance gene to powdery mildew in K8 fit to the inheritance law of quantitative trait.Four QTLs named pm5.1,pm5.2,pm5.3 and pm6.1 for the resistance gene to powdery mildew were detected in this study.pm5.1,pm5.2 and pm5.3 were detected repeatedly in two years and the location for pm5.1,pm5.2 and pm5.3 was consistent.The QTL of pm5.2 accounted for the highest phenotypic variation.Four NBS resistance genes were found in the region of pm5.2.The QTL of pm6.1 located on Chr.6 was a minor QTL.【Conclusion】 The QTL of pm5.2 located on Chr.5 was the major QTL.This resistance gene may belong to NBS resistance gene.The results in this study will be of great benefit to fine mapping and gene cloning for the major QTL of powdery mildew resistance gene,also the results will lay a good foundation for cucumber MAS resistance breeding.