黄瓜白粉病抗性基因的QTL定位

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

【目的】对黄瓜高抗白粉病材料K8进行研究,明确其抗性遗传规律,并完成抗性基因的QTL定位分析,为探索抗病机理和分子标记辅助选择(MAS)育种提供理论依据。【方法】利用黄瓜白粉病致病菌Podosphaera xanthii(syn.Sphaerotheca fuliginea)对K8×K18(感白粉病)杂交后代F2:3家系人工接种鉴定,进行抗白粉病遗传分析。以完成抗病性鉴定的F2和F2:3家系组成的抗感分离群体为研究对象,应用BSA法和2360对黄瓜SSR引物进行SSR分析,采用JoinMap 4.0作图软件和MapInspect软件构建连锁群并完成连锁群与染色体的对应。利用MapQTL4.0软件对白粉病抗性基因进行QTL定位分析。【结果】试材K8所含有的黄瓜白粉病抗性基因符合数量性状遗传的特点。本研究共检测到4个白粉病抗性基因的QTL位点pm5.1、pm5.2、pm5.3和pm6.1,其中,pm5.1、pm5.2、pm5.3在两年中被重复检出,pm5.2位点的贡献率最大,在其所在区域预测到了4个NBS类抗病基因。pm6.1位于黄瓜Chr.6上,是个微效的QTL位点。【结论】位于Chr.5上的pm5.2是黄瓜白粉病抗性基因的主效QTL位点,该抗性基因可能属于NBS类抗病基因。本研究结果为抗性基因主效QTL的精细定位和克隆及MAS抗病育种奠定了良好基础。

[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. Sphaerothecafuliginea） 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 Maplnspect sofrware 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 pro5.1, proS.2, pro5,3 and pro6.1 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 pro5.1, pro5.2 and pro5.3 was consistent. The QTL of pro5.2 accounted for the highest phenotypic variation. Four NBS resistance genes were found in the region ofpm5.2. The QTL ofpm6.1 located on Chr.6 was a minor QTL. [Conclusion] The QTL of proS.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.