一个新的烟草黑胫病主效抗性基因qBS-17精细定位及克隆

The blank shank, caused by phytophthora nicotianae, is one of the most important diseases affecting tobacco (Nicotiana tabacum L.). It is an effective way to prevent the black shank by mining, identification and utilization of resistant genes. A novel QTL for blank shank resistance, named as qBS-17, were identified using a population of F2 derived from a cross between the susceptible cultivar Xiaohuangjin1025 and the resistant source Beinhart1000. Furthermore, the novel QTL has been fine-mapped on the region covering 1.1Mb using BC4F2 and BC4F3 populations and a near-isogenic line (NIL) harboring the target QTL in susceptible parent Xiaohuangjin1025 genetic background was constructed via marker-assisted foreground and background selections. Based on the results mentioned above, we will narrow down the location of qBS-17 by further high-resolution mapping. Combined bioinformatics analysis, RT-PCR technology and association analysis, a candidate gene will be speculated. We will validate effect of qBS-17 by Agrobacterium-mediated transformation. Furthermore, resistant effects and breeding value, haplotype diversity and evolutionary characteristics of qBS-17 will be studied using NIL and mini-core collections, respectively. In addition, we will develop a set of functional molecular markers based on the allelic variation at different loci within qBS-17 for MAS. These results will provide useful information in molecular mechanism and molecular marker-assisted selection for blank shank resistance.

烟草黑胫病是烟草最主要病害之一，发掘、鉴定和利用抗病基因，进而培育抗病新品种是防治黑胫病的有效措施。申请人利用黑胫病感病品种小黄金1025和重要抗源Beinhart1000组合的F2群体定位到一个新的抗性主效QTL，命名为qBS-17；进而利用BC4F2和BC4F3群体将该主效位点精细定位在1.1Mb区间内，目标区段内候选基因22个；同时，构建了携带目标基因的BC5F1近等基因系。本项目在此基础上拟利用培育的次级分离群体，采用图示基因型重叠法进一步缩小基因qBS-17所在区间范围，通过生物信息学、转录水平差异分析和候选基因关联分析等方法确定候选基因，利用农杆菌介导的遗传转化验证候选基因功能，研究种质资源中qBS-17单倍型多样性，开发功能标记，在遗传背景相同的条件下精细评价qBS-17的抗性效应值和育种价值。研究结果将为阐明黑胫病抗性机制和开展抗性分子标记辅助改良奠定基础。

烟草黑胫病是烟草最主要病害之一，发掘、鉴定和利用抗病基因，进而培育抗病新品种是防治黑胫病的有效措施。本项目在此基础上利用培育的BC5F2、BC5F2:3以及BC5F2:4等次级分离群体，采用图示基因型重叠法进一步将控制烟草黑胫病抗性的主效位点qBS-17定位在400Kb左右的内区间范围。通过生物信息学、转录水平差异表达比较和关联分析等方法确定了候选基因为一类编码系统获得性抗性蛋白的Sar8.2基因。该类基因拷贝数的变化是导致不同烟草种质黑胫病抗性差异的分子遗传机制。在不同烟草种质资源中，该基因的拷贝数变化幅度为0-19个。利用自然群体、Magic群体、重组自交系和不同遗传背景的近等基因系等不同遗传材料，系统评价了该主效位点的遗传效应和育种价值。结果表明，qBS-17基因在烟草黑胫病抗性育种中起到重要作用，在大田条件下有效的降低黑胫病的发生，具有重要的育种价值。相关研究结果为阐明黑胫病抗性机制和开展抗性分子标记辅助改良奠定了基础。