“特特普”基因组中抗稻瘟病基因的系统调查

Current research indicates that plant resistance can recognize pathogen effectors and then induce the resistance. Now the question raised is that how to explain the resistance of the varieties by using the knowledge of molecular resistance mechanism. To address this question, it is essential to know whether the resistance of a cultivar is determined by several major resistance genes or by a combination of many genes resistant to different pathogen isolates. Here, we design a study to detect the rice blast resistance genes in a series of cultivars bred from the same resistance resource, Tetep. Tetep is a highly resistant cultivar which has been widely used as the resource in rice resistance breeding and from which many resistance cultivars have been bred. Therefore, we could detect how many and what kind of resistant genes are derived from Tetep in its offspring. By sequencing Tetep and its resistant offspring, we can identify the chromosome segments in the offspring which come from Tetep and detect the numbers and types of resistance genes in these segments. Then we can clone, transfer and screen these genes to identify their resistance and test the questions raised above. As results, we could obtain several major resistance genes and the combinations of resistant genes, which are potential to be applied in rice breeding. Such genes or combinations in its resistant descendants could be the key factors to understand the underlying mechanism of the resistant cultivars and the guidelines to use these gene in production.

植物的抗病基因可识别病菌的特定诱导物，进而引起植株的抗病性。这种机制在基因层面已经很清楚，但怎样用它们来解释品种的抗病性尚待研究。决定品种抗性究竟是几个主效的抗病基因，还是许多个抗不同病菌小种基因的组合？这种田间抗病机制，可以通过找出育种上来自同一抗源的系列品种的抗病基因来检验。比如水稻 “特特普”是一个高抗稻瘟病的抗源，用它育成了许多高抗品种。本项目就是利用这些遗传材料，从中找到特特普在杂交育种过程中转移到抗病后代中的抗病基因。通过对特特普及其抗病后代的基因组测序，找出抗病后代中来自特特普的染色体区段，评估这些区段中的抗病基因数量和种类，进而抽样鉴定这些基因的抗病性，最终从基因层面检验抗源品种遗传给抗病后代的、在生产上可以应用的抗病基因及其组合。抗病后代共有的抗病基因或组合，可能就是决定品种抗性的关键，也是生产上直接应用抗病基因的理论基础，更是理解品种田间抗性形成的重要科学依据。

稻瘟病是水稻主要的病害之一，对其安全生产够成重要的威胁，而防治稻瘟病最经济有效的手段是利用水稻自身的抗性基因。目前，虽然已经有不少抗稻瘟病基因被鉴定与克隆，但相比于提供抗病基因的亲本品系而言，这些基因存在抗谱窄、抗性持续时间短的缺点，很难直接应用于生产实际，究其根本原因在于，我们对植物自身广谱高抗的内在机制缺乏了解。本项目以广谱高抗的水稻品种特特普及其抗病后代为研究材料，通过二代测序，基因组重组装，系谱追踪，功能验证等方法深入探讨特特普具有持久、广谱抗性的抗性机制。本项目完整拼装了特特普的基因组并对其抗病基因组（NLR）进行了进化分析，通过高通量克隆的方法，成功克隆并完成了219个NLR基因的功能验证，实验结果表明41%的NLR基因对特特普的抗性具有贡献，且存在抗性冗余的现象，但广谱高抗的基因数目不多，未发现能抗所有稻瘟病菌株的NLR基因位点。对特特普抗性育种系谱的基因普查与追踪发现，多基因对整体抗性具有贡献。由此说明，抗性基因的功能冗余、多抗性基因的参与与互作是特特普具有广谱持久抗性的主要原因。本项目利用田间抗性材料及其育成抗性品系为材料，从全新的角度探讨了植物持久抗性的特点与机制，为作物精准抗性育种提供了可行的范例与方向。