基于渐渗系的甜椒疫病抗性遗传解析及主效QTL精细定位

Pepper is an important vegetable around the world. Phythophtora blight is a kind of destructive fungus disease for pepper production. The number of pepper germplasm with highly resistance to phythophtora blight is small. And these germplasms are always hot peppers. There is lack of sweet pepper with highly resistance. The resistance can be lost when it is transferred from hot pepper to sweet pepper. Previous studies about the inheritance and relevant molecular researches for the resistance in pepper were all focusing on hot peppers. And the inheritance was still in dispute. There are no deep researches on molecular markers and QTL mapping for the resistance. We have not seen one report about gene fine mapping for the resistance to phythophtora blight in pepper. The marker assisted selection (MAS) breeding program about the resistance to phythophtora blight in sweet pepper was not conducted because of no proper experimental materials. We bred a new sweet pepper in-bred line named N1345 with highly resistance to phythophtora blight after several years' work. It was the first time to report a sweet pepper with high resistance to phythophtora blight. Using this precious material as one parental line, we aimed at constructing an introgression lines (ILs). ILs based on a reference molecular linkage map is the best plant materials for accurate QTL mapping and fine mapping. In this project, the inheritance and QTLs for the resistance genes in N1345 will be made clear and mapped using ILs as materials. And the analysis of genetic effect and fine mapping for major QTL will also be conducted. This study is significant in making clear the inheritance and the molecular mechanism of the resistance to phythophtora blight in sweeet pepper and it can provide academic guidance and practical molecular markers to the resistance breeding program.

甜（辣）椒是一种重要的蔬菜作物，疫病是危害其生产的毁灭性病害。高抗疫病的甜（辣）椒种质资源少，且多为小果型辣椒材料，甜椒高抗疫病资源严重缺乏。而依赖于辣椒资源进行甜椒抗疫病转育多存在抗性丢失现象。前人关于疫病抗性及相关分子研究主要集中于辣椒，且在遗传上存在较大争议，在分子标记和QTL定位方面进展缓慢。至今未见甜（辣）椒疫病抗性基因精细定位研究的报道。由于缺乏合适的试验材料，甜椒疫病抗性分子育种没有深入开展。本项目组在国内外首次报道了高抗疫病的甜椒材料N1345，并利用该材料构建了渐渗系（ILs）。基于完全连锁图谱的ILs是进行QTL准确定位与精细定位等系列后续分析的理想材料。本项目拟利用ILs材料，完成抗性QTLs的准确定位，并对主效QTL进行遗传效应解析和精细定位。本研究对于明确甜椒疫病抗性的遗传及内在分子机制具有重要意义，同时可为抗病MAS育种提供理论依据和实用分子标记。

辣椒是世界范围内广泛栽培的一种重要蔬菜作物。高密度辣椒种内完全连锁遗传图谱的构建对于辣椒育种具有实际应用价值。然而辣椒上以PCR为基础的SSR、Indel标记信息有限，辣椒种内完全连锁图谱的饱和度有待提高。我们先期利用NCBI非冗余辣椒EST数据库，共开发可用的EST-SSR标记902个，后基于辣椒基因组信息，共开发辣椒SSR位点177587个，其中包括基因区上下游SSR标记位点9182个；开发稳定可靠的InDel位点4497个。从中选出平均分布于12条染色体的3356对基因组SSR引物和1400对InDel引物，以PM702和FS871为双亲构建的F10代RIL群体为作图群体，同时利用先期开发的902个EST-SSR标记、发表的524个SSR标记和299个conserved ortholog sets标记(COSIIs)，进行辣椒种内高密度遗传图谱的构建。最终获得了一张包含12个连锁群和708个分子标记, 长度为1260.00cM, 平均图距为1.78cM的辣椒种内高密度完全连锁遗传图谱。并对辣椒的segregation distortion region (SDR)进行了分析，共检测到了20个SDR。该图谱是迄今为止包含SSR标记和InDel标记最多，饱和度最高的一张辣椒种内高密度完全连锁遗传图谱，对辣椒分子育种具有重要意义。利用建成的辣椒完全连锁遗传图谱，结合3次不同季节辣椒疫病抗性的表型数据，采用MapQTL5.0软件进行多座位QTL模型(Multiple-QTLmodel，MQM)检测。结果共检测到15个与辣椒疫病抗性相关的QTLs，贡献率为8.1-73.3%，表型贡献率≥10.0%的主效QTLs有6个，约占QTL总数的40%，经3次鉴定可重复检测出的QTLs有2个，为位于第5条染色体上的qrb5-2和qrb5-3 ， qrb5-2的相邻最近的标记为GI1389和GI1402，qrb5-3相邻最近的标记为GI1418和ZS70269,可用于辣椒疫病抗性分子育种。