辣椒抗CMV主效QTL qcmv11.2的精细定位及候选基因分析

Cucumber mosaic virus (CMV) is one of the most destructive viruses in pepper. It is very important to identify the quantitative trait loci (QTLs) conferring the resistance to CMV in pepper for breeding of resistant pepper varieties and for the understanding of the mechanism of quantitative resistance. A major QTL, qcmv11.2 on pepper P11 chromosome associated with CMV resistance was identified during two SSR markers in previous study. The near isogenic lines (NILs) XJ0630-qcmv11.2 was also developed by backcross breeding and marker-assisted selection, in which only the QTL qcmv11.2 was introgressed from the donor parent. On the base of invaluable sequence information of pepper genome, a set of molecular markers at the chromosome region covering the qcmv11.2 interval will be developed in the present study. The new developed markers will be used to construct the high-density linkage map covered the resistant QTL. Polymorphism markers in the original interval of qcmv11.2 will be used to develop a set of chromosome segment substitution lines (CSSLs) for next step of fine mapping. By correlating the result of phenotype of each CSSLs and its genotype profile, the qcmv11.2 will be fine localized to a region. Identifying the target quantitative genes in the region has become practical in pepper by candidate gene analysis. The expression of the candidate genes will be analyzed with RT-PCR. Nucleic difference during pepper materials with different resistance levels will be analyzed. The results in our study will accelerate the practical breeding use of qcmv11.2 in resistance to CMV in pepper by MAS, and the cloning and related resistant mechanism analysis of qcmv11.2.

黄瓜花叶病毒病是辣椒生产上的最主要病害之一，深入挖掘和分离抗病资源中的抗性QTL，对辣椒抗CMV育种及相关抗性机制的解析具有重要意义。本研究前期已将辣椒抗CMV主效QTL qcmv11.2定位在P11染色体两个SSR标记间，并构建了覆盖目标QTL的近等基因系XJ0630-qcmv11.2。在前期研究的基础上，本项目拟结合辣椒基因组序列开发新标记，进一步构建目标QTL染色体区段的高分辨率图谱；应用目标片段内的多态性标记进行筛选，构建抗性QTL区段的染色体单片段叠代系次级群体，并对次级群体进行分子和表型鉴定，精确定位qcmv11.2物理区间；预测候选基因，进行候选基因表达分析以及不同抗性辣椒种质间的核酸差异分析。研究旨在开发与qcmv11.2更紧密连锁标记，并从分子水平上初步探讨不同抗性品种间的差异，为加速qcmv11.2在辣椒抗CMV分子辅助选择育种中的应用和后续深入解析抗性机制奠定基础。

黄瓜花叶病毒病是辣椒生产上的最主要病害之一，深入挖掘和分离抗病资源中的抗性QTL，对辣椒抗CMV育种及相关抗性机制的解析具有重要意义。本研究利用覆盖目标QTL的近等基因系XJ0630-qcmv11.2群体，结合辣椒基因组信息和双亲简化测序信息开发新标记，进一步将qcmv11.2区间定位在标记Marker5510971和Marker5227451间2.05cM的区间内，物理区间为19.403-24.467 Mb；在区间内进一步开发了10对SNP-HRM引物，通过标记进行重组单株筛选，将qcmv11.2定位在SNP标记MSNP11-13和MSNP11-10之间，区间内共有4个连锁标记。对候选区间进行预测分析，区间内共有39个已注释的基因；根据区间定位的峰值及父母本间的SNP信息，选择其中15个基因进行表达分析，推测其中3个可能是与抗CMV相关的抗性基因。利用连锁标记MSNP11-7对3份不同抗性水平的材料进行PCR扩增后测序，结果表明3份材料间存在着序列差异，这可能是引起抗性水平差异的原因之一。本研究最终获得了4个与qcmv11.2更紧密连锁标记，并初步探讨不同抗性品种间的差异，为加速qcmv11.2在辣椒抗CMV分子辅助选择育种中的应用和后续深入解析抗性机制奠定基础。