玉米抗灰斑病主效QTL-qRgls2的克隆和分子机理探索

玉米灰斑病由玉蜀黍尾孢菌侵染引起，是一种世界性的玉米病害，危害严重。该病最早在美国发现，近年来在我国各玉米产区迅速蔓延，已成为玉米生产上最严重的病害之一。现有的防治措施，如喷施杀菌剂、翻耕、间混作等，效果均不理想，而最经济有效的途径就是要培育和推广抗病品种。在前期研究中，我们在热带血缘材料中发现了一个抗灰斑病的主效QTL，qRgls2，它位于5号染色体着丝粒附近，能稳定提高抗病率20%以上，已被限定在1Mb范围内。本项目将采用精细定位、关联分析、表达研究、预测基因结构比较等手段确定候选基因，用转基因方法进行功能互补验证，克隆抗病基因。在此基础上，研究抗病基因的结构、亚细胞定位、时空表达、诱导表达和编码蛋白的功能，进而深入分析近等基因系抗病反应的转录组特征、与抗病基因互作的上下游蛋白，来阐述抗病的分子机理和调控途径。最后，利用抗病基因的序列信息开发分子标记，为分子育种改良玉米抗性服务。

Gray leaf spot (GLS), caused by Cercospora zeae-maydis or Cercospora zeina, is a devastating maize disease worldwide. GLS was first discovered in USA, and it currently spreads fastly to all maize growing areas in China and becomes one of the most destructive maize diseases. The current regular disease control methods, such as fungicide spray, conventional tillage, and intercropping, is incapable to effectively contain the disease. Hence, development and deployment of resistant cultivars is the most ecomomic and efficient measure to control the GLS. In our previous study, we have discovered a major resistance QTL, qRgls2, from a tropical maize line, which is located within a region of 1Mb adjacent to the centremere of chromosome 5 and could enhance the resistant percentage by more than 20%. In the current project, we will conduct fine-mapping, association mapping, expression profiling, and architecture analysis of predicted genes to determine the candidate gene, and then use transformation-mediated complementary fuctional test to validate the resistance gene. With the availablity of the resistance gene, we will analyze the gemonic structure, temporal and spatial expression profile, induced expression, and protein function of the resistance gene. We will study the transcriptome profiles between resistant and susceptible near isogenic lines, and interaction proteins involved in the GLS resistance to illustrate molecular mechanism and regulation pathways. Finally, we will develop molecular markers on sequence information of the resistance gene, which could be readily used in molecular breeding to improve maize resistance to GLS.