一个新的白菜抗根肿病隐性QTL位点Br-crl的精细定位与候选基因鉴定

Clubroot is becoming one of the most damaging disease to the production of Chinese cabbage. Plasmodiophora brassicae has a wide range of hosts, and pathotypes are significantly differentiated. Therefore, exploring new clubroot resistance (CR) genes for durable and broad-spectrum resistance and cultivating resistant varieties become a safe and effective way to reduce the damage. In a previous study, we screened our germplasms and mapped a novel recessive QTL locus Br-crl which is resistant to the race 4 and 7 of P. brassicae. The Br-crl was located on chromosome A02 of B. rapa within 642 kb region, which is the only recessive gene until now. In this project, we intend to collect a wide range of P. brassicae of clubroot to detect the broad-spectrum resistance of Br-crl to different races. Furthermore, constructing BC1F2 segregation population and developing high-density SNP markers by resequencing of the parents will be carried out. Then, the candidate genes will be identified based on bioinformatics prediction, gene sequence analysis, qRT-PCR analysis and Arabidopsis thaliana transformation. The co-segregation SNP markers of Br-crl will also be established for the high-throughput molecular marker-assisted breeding system. The results of this study will not only lay the foundation for revealing the recessive resistance mechanism of Br-crl, but also provide a theoretical basis for the broad-spectrum disease-resistant breeding of Chinese cabbage.

根肿病已成为威胁大白菜等芸薹属作物的最严重病害之一。目前白菜主栽品种抗源单一，而病原菌生理小种分化激烈导致其防控难度极大。挖掘广谱抗病基因，培育持久抗病新品种是降低病害损失的有效途径。本项目组通过规模化资源筛选，在欧洲芜菁中发掘了一个兼抗4号和7号生理小种的隐性抗病QTL位点Br-crl，并将其定位于A02染色体642kb区间内，是芸薹属作物中定位的首个隐性抗根肿病基因位点。本项目拟广泛收集我国大白菜主产区根肿病菌，研究Br-crl对不同生理小种的抗性反应和抗性程度，分析其是否具有广谱抗性；通过构建BC1F2分离群体和高通量SNP分型技术，精细定位Br-crl；基于生物信息、转录分析及转化拟南芥等鉴定抗病候选基因，并开发与Br-crl共分离的SNP标记。研究结果不仅为揭示Br-crl的隐性抗病机制奠定基础，也为培育持久广谱抗根肿病的大白菜品种提供技术支撑。

白菜我国第一大蔬菜作物，是城乡居民的“当家菜”。根肿病已成为威胁大白菜等芸薹属作物的最严重病害之一。目前白菜主栽品种抗源单一，而病原菌生理小种分化激烈导致其防控难度极大。挖掘广谱抗病基因，培育持久抗病新品种是降低病害损失的有效途径。本项目组通过规模化资源筛选，在欧洲芜菁中发掘了一个兼抗4号和7号生理小种的隐性抗病QTL位点Br-crl，并将其定位于A02染色体642kb区间内，是芸薹属作物中定位的首个隐性抗根肿病基因位点。本项目拟广泛收集我国大白菜主产区根肿病菌，研究Br-crl对不同生理小种的抗性反应和抗性程度，分析其是否具有广谱抗性；通过构建BC1F2分离群体和高通量SNP分型技术，精细定位Br-crl；基于生物信息、转录分析及转化拟南芥等鉴定抗病候选基因，并开发与Br-crl共分离的SNP标记。研究结果不仅为揭示Br-crl的隐性抗病机制奠定基础，也为培育持久广谱抗根肿病的大白菜品种提供技术支撑。.项目组通过QTL和BSA联合作图分析，结合5000株的F2群体将“感病”基因Br-crl 精细定位于白菜A02染色体着丝粒附近294.6kb（包含32个基因）。通过抗感病材料转录组、基因序列比对和启动子活性分析表明富含亮氨酸重复的受体激酶Br-crl是抗病候选基因。研究发现抗感材料Br-crl的启动子序列显著不同，抗病材料有197bp插入；感病材料接菌后表达量明显上调，抗病材料表达无变化；GUS实验表明抗病材料启动子活性极弱。最后，我们将197bp差异序列分别转化成KASP和InDel标记，在DH群体、F2群体和自然群体中均表现为共分离，可以用于辅助育种。此外，项目组完成了芸薹属根肿菌4号生理小种基因组组装和注释。隐性机制的解析将丰富对于植物-病原菌互作分子机制的认识，为抗根肿病分子育种提供理论依据。广谱、持久抗根肿病材料的创制，将提高原始创新能力，加强白菜种质资源挖掘与利用。