一个新的水稻籽粒垩白度和透明度QTL（qDC10/qET10）的精细定位

Rice grain chalkiness was one of the most important evalutation indexes for rice appearance quality. BC2F2 segregating population derived from rice main parent combination Teqing/IR24 was used to validate a new and important pleiotropic effects QTL located on the long arm of chromosome 10 and further delimited it into a more precise region, in which, degree of chalkiness and endosperm transparency were chosen as target traits. The important recombinant plants were picked out from BC3F2 population to construct chromosome segment substitution lines set and to develop BC3F3 strains. According to the phenotypic data of BC3F4 plants derived from stable genetic plants in BC3F3 population and the genotype data of plants in chromosome segment substitution lines set, the QTL confering rice grain degree of chlkiness and endosperm transparency were fine mapped.The public DNA sequnce data and candidate genes information were utilized to get the target candidate gene in the fine mapping intervals. The conclusion of this study laid important basis for the following study about cloning the target gene and illuminating the formation of molecular mechanisms underlying rice grain chalkiness and endosperm transparency, which was of great significance for improving China rice appearance quality.

水稻籽粒的垩白性状是我国稻米外观品质重要的评价指标之一。项目拟在前期研究基础上，以水稻骨干亲本特青和IR24为原始亲本，垩白度与透明度为目标性状，利用BC2F2分离群体验证位于第10染色体长臂一个新的重要的功能多效性QTL，并进一步缩小其所在的分子标记区间。在BC3F2群体中挑选重要交换单株构建覆盖目标区间的染色体片段代换系群，根据中选交换单株的BC3F3株系内稳定单株所衍生的BC3F4株系表型平均值数据，实现目标区间内籽粒垩白度和透明度QTL精细定位，并利用公共DNA序列资源和候选基因信息分析，获得精细定位区间内与目标性状遗传控制相关的候选基因。研究结论为后续的目标基因克隆，阐明水稻垩白和透明度的形成分子机制奠定重要基础，这对改良我国水稻稻米外观品质具有重要意义。

垩白和粒型是水稻两个重要的外观品质性状，是决定稻米市场分级的重要指标。项目针对前期试验结论，在水稻第10染色体长臂SSR分子标记区间RM6704-RM228内存在一个控制包括粒长、粒宽、千粒重、垩白米率、垩白度、透明度、糙米率多个重要农艺性状的微效QTL簇，命名为qPGC/qDC。利用从特青/IRBB组合发展的重组自交系群体中筛选到的一个RM6704-RM7300为杂合，染色体组其他区域基本为纯和的剩余杂合体（RHL）RHL-100，自交获得（RHL-100）-F2群体，结合区间内分子标记基因型数据和群体表型数据分析，目标区间缩小至RM3773-RM228内。以特青为母本，IR24为父本，针对RM3773-RM228区间，在分子标记辅助选择下，连续回交构建遗传分析群体。利用190个BC2F2株系所对应的BC2F2:3家系群体基因型和表型数据验证了qPGC/qDC。从3,432个BC4F2单株中种筛选出4个BC4-F3交换单株所对应的BC4-F4家系基因型和表型数据，分析qPGC/qDC所在的染色体上物理位置，将其界定在分子标记Qpcg-48-Qpcg56 区间51.42kb范围内，对应于水稻粳稻品种日本晴染色体物理位置21,690,001bp和21,741,428bp。qPGC/qDC对粒长、粒宽、千粒重、垩白米率、垩白度和透明度均起微效作用，除透明度增效等位基因来自IR24外，其他5个性状增效等位基因均来自特青。根据水稻基因组注释计划网站(http://rice.plantbiology.msu.edu/index.shtml)提供的信息，区间内存在9个编码功能蛋白的候选基因，其中3个为专一性脂类转运蛋白（nsLTPs）前体基因构成了一个串联重复，与植物种子贮藏有关。这些结果为分离鉴定qPGC/qDC，剖析其水分子遗传基础提供重要的理论依据和实践基础。