大豆抗孢囊线虫的超亲遗传机制及抗性分子标记研究

The soybean cyst nematode (SCN), Heterodera glycine, causes disastrous damage in soybean (Glycine max) worldwide. Host-plant resistance is the most economically effective approach for SCN control. However, limited SCN resistance source of the major commercial cultivars and multiple SCN races in the field result in resistance loss. Thus it is urgent to develop soybean varieties with multiple resistance to SCN races. Our studies found that higher resistant and susceptible progenies than both parents (called transgressive segregation) occurred in one population of chromosome segment substitution lines (CSSL).The CSSL population was developed from one of the major commercial cultivars in Northeast China. In order to utilize these transgressive lines, this project will detect SNP variation sites among parents and DNA bulks using the combination of whole-genome resequencing with bulk segregant analysis (BSA) (QTL-seq). SNP molecular markers associated with resistance will be obtained using bulked-associated SNP-index method and the certain area linked to resistance genes will be determined. The potential genes linked with resistance will be identified through SNP function-association analysis. PCR-based CAPS/dCAPS markers will be developed for marker-assisted selection in breeding program. The identified resistance region will be fined mapping with screening previously published and new developed molecular markers. Through phenotypic and genotypic screening, varieties with multiple resistance to SCN races will be found. These QTL analyses will clarify the mechanism of transgressive resistance, utilize the transgressive resistance sources, increase field durable resistance and expedite molecular-assisted breeding program.

大豆孢囊线虫病（SCN）是一种世界性的毁灭性大豆病害，寄主抗性是最经济有效的防治策略，但目前的品种抗性单一，且田间存在多种生理小种，抗性极易丧失，急需培育多抗品种。野生大豆与主栽品种（轮回亲本）所构建的高世代染色体片段代换系群体，出现了后代超出亲本的超抗和超感SCN的个体植株。为充分利用这些抗性资源，本项目拟利用全基因组重测序技术和集群分离分析法相结合（QTL-seq），定位亲本和子代混池的SNP等变异位点，通过混池关联分析（SNP-index）获得SNP分子标记，将抗病基因定位到一定区域；通过SNP功能关联分析，鉴定与抗病基因相关联的基因；把SNP标记转化成PCR基础上的CAPS/dCAPS标记；然后利用已知的引物精细定位这些抗性区域；通过表型筛选和基因型差异分析，鉴定多抗品种及其关联的QTLs，进而阐明超亲抗性机制，开发利用超亲抗性资源，增加田间持久抗性，加速SCN分子抗病育种进程。

大豆孢囊线虫（SCN，Heterodera glycines）病是一种世界性的毁灭性大豆病害。基于目前抗性资源缺乏和抗性单一等问题，筛选和培育多抗品种是当务之急，解析抗性机制使已有的抗性种质资源能够得到充分利用，加速分子辅助育种。本研究首次利用162个BC3F7-BC7F3大豆染色体代换系群体CSSLs（Glycine max绥农14×野生型G. soja ZYD00006）开展了每克根重SCN的孢囊数（cysts per gram root，CGR）的抗性评价和QTL定位研究，表型鉴定结果表明表型分布广泛，SCN5号生理小种 雌虫指数FI和CGR都呈现出了超亲遗传现象，FI与CGR的相关性比较低（R2=0.0018），CGR与根重的相关性较高（R2=0.5424）。对代换系群体进行全基因组重测序，使用K*单标记检测和MQM方法共鉴定得到38个QTLs（FI和CGR）覆盖了大豆20条染色体，双亲对超亲遗传都有贡献。研究发现在缺少SCN主要抗性基因（如rhg1和Rhg4）的情况下，综合考虑FI、CGR及根重三者有利基因的组合可以有效抑制线虫繁殖，同时发现对SCN有耐性并适合于东北种植的具有绥农背景的代换系株系具有潜在的应用价值。通过筛选东北的抗性种质资源，发现了新的抗性背景资源，构建了F2分离群体，表型筛选和靶向测序基因型检测（10K SNP芯片）进一步证实了超亲遗传抗性是来自双亲的不同位点的结合。对亲本三代全长转录组测序和标记区间共有的差异表达基因注释，发现了一些转录因子与大豆的抗性和防御有关。所鉴定的抗性分子标记能够有效的预测植株的抗感。综上所述，本研究所筛选的抗性种质资源、确定的抗性单倍型、鉴定的分子标记能够加速东北大豆抗孢囊线虫分子辅助育种，通过解析大豆-孢囊线虫复杂的互作机制，从而丰富了线虫-植物互作知识。