基于CUBIC群体剖析玉米南方锈病抗性的遗传结构

Southern corn rust (SCR) is one of the devastating and widespread fungal diseases in corn production area. Genetic dissection of resistance to SCR and isolation of the resistance genes will play an importance role in understanding the mechanism of disease resistance and utilization in maize breeding program. It has been reported that all major QTLs resistance to SCR located in bin 10.00/01 at chromosome 10. However, the resistance of this locus has a tendency to lose in application process. It is necessary to identify new resistant loci and systematically dissect genetic architecture of resistance to SCR. Therefore, we used multiple inbred lines to developed a new genetic population, Complete-diallel plus Unbalanced Breeding-like Inter-Cross (CUBIC), which contained 1404 lines. This population were genotyped by high-density SNP markers and phenotyped in multiple environments. We will comprehensively dissect the genetic architecture of resistance to SCR by association analysis. Further, based on the detected QTLs, we will pick out 2-3 major QTLs to isolate the candidate genes and develop functional markers through bioinformatic analysis and molecular biological methods. This project plans to screen the high resistance lines and analyze the characteristics of pyramiding multiple resistant genes to obtain the best type of pyramiding genes, which provide practical guidance and lay a foundation for molecular breeding on maize disease resistance.

玉米南方锈病是玉米生产上普遍发生的真菌性病害，解析病害抗性的遗传基础，分离主效抗病位点，对玉米抗病育种和解析抗病分子机制都有重要的意义。已有研究表明抗南方锈病的主效位点均集中在玉米第十号染色体短臂bin10.00/01上，然而在生产上该位点的抗性易丧失，因此需要鉴定新的抗病位点，并全面的解析南方锈病抗性的遗传结构。为此，本研究采用1404份家系构成的多亲本高世代互交群体（CUBIC），构建高密度的分子标记图谱，并完成多年多点的群体南方锈病抗性的鉴定。本研究拟通过关联分析在全基因组范围鉴定与抗性相关联的位点，剖析南方锈病抗性的遗传结构。本项目拟采用生物信息学和分子生物学等手段挖掘和验证2-3个主效抗病基因，并开发功能分子标记，筛选群体中高抗材料，分析抗病位点聚合特点，获得最佳的抗病位点聚合类型，为玉米抗病分子育种提供理论依据和实践指导。

玉米南方锈病是我国黄淮海平原夏播玉米区和南方丘陵玉米区的主要玉米病害之一，严重威胁我国玉米产区的品质和产量。本项目以玉米CUBIC群体为基础，调查南方锈病抗性，采用两种统计分析方法开展全基因组关联分析，分别检测到25个sQTL和41个hQTL，最终合并成59个抗南方锈病位点，其中包括9个主效位点，该性状是由几个主效抗病基因和多个微效基因共同控制。与已发表的QTL比较，鉴定出40个新的抗南方锈病位点，包括4个主效抗病位点。进一步分析发现微效抗病位点而不是主效位点影响玉米农艺性状，其中16个抗病位点影响玉米开花期，19个位点影响玉米株型，9个抗病位点影响玉米产量相关性状。通过基因聚合分析，发现同时聚合5个主效抗病位点能显著提高玉米南方锈病抗性且不影响玉米开花期和产量相关性状。通过候选基因关联分析、表达量分析和基因编辑等方法和技术挖掘chr2、chr7、chr10染色体上主效抗病位点的候选抗病基因，田间抗病性试验初步验证ZmHsp和ZmPept候选基因的抗病功能。本项目研究结果将有助于我们深入理解玉米南方锈病抗性的遗传基础，同时为玉米抗病分子育种提供重要价值。