冬瓜果重主效QTLfw3.1的精细定位及候选基因克隆

Fruit weight is the most important component of yield in fruit vegetables, and has been the research hot spot of breeders for a long time. Wax gourd (Benincasa hispida Cogn.) is a significant vegetable crop in Cucurbitaceae. The fruit weight of different types showed remarkable difference, which made it an ideal material for fruit weight study. Previously, based on the high density genetic map of wax gourd, a major QTL locus with a phenotypic variance rate of 15.8% in the third linkage group was obtained and named fw3.1. In this project, based on the results of genome re-sequencing, we used the F2 population as materials to construct the encrypted marker genetic map by SSR and InDel markers. Furthermore, in order to fine mapping fw3.1, the second population derived from the remaining hybrid (RHL) was used to screen recombinant strains. Subsequently, according to the whole genome sequence, gene structure and protein function annotation information of wax gourd, the candidate genes were predicted in the fine mapping region, and the expression of these genes were analyzed by qRT-PCR technique to confirm the target gene. The results of this study will lay the foundation for related gene mining of fruit weight, molecular breeding and fruit development research, which has important theoretical and practical value.

果重是果菜类蔬菜最重要的产量构成性状，长期以来一直是育种家的研究热点。冬瓜是葫芦科重要蔬菜作物之一，不同类型冬瓜果重差异显著，是果重研究的理想试材。项目组前期基于冬瓜高密度遗传图谱，获得一个位于第3连锁群，对果重表型变异贡献率为15.8%的主效QTL位点，并将其命名为fw3.1。在此基础上，本项目拟以F2群体为材料，基于基因组重测序结果，利用SSR和InDel标记构建初定位区间的加密遗传图谱。进一步利用剩余杂合体（RHL）衍生的次级群体筛选重组株，精细定位fw3.1。随后，根据冬瓜全基因组序列、基因结构和蛋白功能注释信息，在精细定位区间内预测候选基因，并利用qRT-PCR技术分析候选基因的表达差异，确定目的基因。本研究结果将为冬瓜产量相关基因挖掘、分子育种及果实发育等研究奠定基础，具有重要的理论和应用价值。

果重是重要的产量构成性状，在果实发育研究中常被用来衡量果实的大小。不同冬瓜材料的果重差异十分显著，大果型冬瓜单果重可达50kg，而小果型仅有1kg左右，材料间的显著差异为果重基因挖掘和果实发育研究奠定了基础。项目前期通过大果亲本B227与小果亲本B214构建的高密度遗传图谱，获得了一个冬瓜果重主效QTL，本项目在此基础上，进行了初定位区间的标记加密、区间内候选基因筛选等工作。同时开展了冬瓜果重相关基因的全基因组驯化、改良扫描，获得了位于10号染色体的候选基因Bhi10G001538（与黄瓜果实大小基因Csa2G258100同源）和Bhi10G000196（与番茄果实大小基因SlFIN同源）。此外，我们利用大果亲本B227与另一个小果材料HF3构建了一个新的果重分离群体，通过BSA-Seq及包含1486个单株的F2分离群体进行基因定位，将果重基因定位在10号染色体96.36kb区间内，区间内包含两个注释基因，并对这两个基因进行了克隆、表达量分析及亚细胞定位。本项目通过精细定位、全基因组扫描等方法获得了4个冬瓜果重相关的候选基因，并对候选基因进行了表达量分析、亚细胞定位、瞬时表达等研究，为后续开展果重基因功能及调控机制研究奠定了基础。