水稻繁殖期耐盐种质资源的鉴定及耐盐基因挖掘

Salt damage is one of the most important abiotic stresses, which seriously affects rice development and grain yield. At present, the planting area of saline land in China is about 100 million hm2, and about 20% of the area of paddy field is affected by salinity. The reproductive stage of rice development is very sensitive salinity. Salinity at the reproductive stage seriously reduced grain yield. The adoption of salt tolerant varieties is the most economic and effective option for reducing the effect of salinity. The limited genetic diversity of current breeding populations greatly slows down the progress of breeding for improved salinity tolerance. Therefore, it is paramount that new genes or new alleles of known genes for tolerance are identified and introduced into breeding populations.To identify germplasm and discovery new genes/alleles for salt tolerance we identified 10000 rice germplasm from IRRI genebank using the recently developed Focused Identification of Germplasm Strategy. Screening for salt tolerance at seedling stage identified more than 300 germplasm with good tolerance. These 300 accessions and 100 accessions that are sensitive to salt and from a wide range of geographic locations will be used as association panel in the proposed project. This panel has been deeply re-sequenced. Accessions with good tolerance at reproductive stage will be used to develop bi-parental populations for linkage mapping through QTL-seq. Accessions with contrasting tolerance will be used in RNA-seq experiments. It is expected that the combined use of genome-wide association, QTL-seq and RNA-seq will allow rapid identification of tolerant germplasm, chromosomal regions and candidate genes for tolerance. Selected candidate genes will also be validated.

盐害是重要的非生物胁迫之一，严重影响水稻的生产发展。目前，我国盐碱地种植面积约 1 亿hm2，而受盐害影响的稻田耕地面积约为五分之一。繁殖期作为直接影响水稻产量的关键时期，一旦受到盐害将大大降低产量。培育耐盐水稻品种，是有效抵御盐害、提高水稻产量行之有效的办法。当前，育种遗传基础狭窄是育种进展的主要制约，迫切需要导入新基因或引入新的等位变异。项目依托实验室利用国际上最近提出的以目标性状为导向的种质鉴定策略，从国际水稻研究所国际基因库中获得10，000份水稻种质资源并进行苗期耐盐性鉴定，获得了300多份苗期耐盐材料，这些材料和来源广泛的100份苗期盐敏感材料形成本项目的材料基础（关联分析群体，连锁分析群体的亲本）。目前，已经完成这些材料的重测序。本项目将利用全基因组关联分析、QTL-seq及转录组测序技术，挖掘繁殖期耐盐基因，为培育水稻繁殖期耐盐品种提供优异的耐盐资源。

水稻是盐敏感作物，特别是在繁殖期受到盐害，将大大降低水稻产量。目前，关于水稻耐盐性的研究几乎都集中在苗期，而对繁殖期耐盐性的研究较少。因此，挖掘水稻繁殖期耐盐基因、培育耐盐水稻品种，是有效抵御盐害、提高水稻产量行之有效的办法。本项目前期利用国际上提出的以目标性状为导向的种质鉴定策略，从国际水稻研究所国际基因库中获得10，000份水稻种质资源并进行苗期耐盐性鉴定，获得了300多份苗期耐盐材料，这些材料和来源广泛的100份苗期盐敏感材料形成本项目的材料基础。本项目我们对400份材料9个繁殖期耐盐性状进行了鉴定，结果表明，除了茎中钾离子含量（CKC）和茎中钠钾离子含量比值（CNKR）外，其他7个性状均表现出正态分布。我们对9个繁殖期耐盐性状进行全基因组关联分析，共检测到了20个显著的QTLs，分别定位在1，2，3，4，5，6，7和11号染色体上。根据苗期和繁殖期耐盐鉴定的结果，我们选择耐盐品种Bhera Dawa与盐敏感品种IR36进行杂交构建F2群体用于QTL-seq和QTL定位分析。通过对F2群体的QTL-seq分析，共检测到了10个QTLs，分别定位在1，3，7，11和12号染色体上。同样，通过对F2群体的QTL定位分析, 共检测到了3个QTLs，分别定位在1和9号染色体上。综合上述三种方法的结果，我们对位于1号染色体上的qLKC1进行进一步分析，由于该QTL接近已知耐盐基因SKC1位置，因此，我们认为SKC1基因可能影响繁殖期耐盐性。通过分析400份材料SKC1基因的单倍型我们发现SKC1基因有24种单倍型，其中3种单倍型（H1，H14和H18）的Na+/K+要比对照品种Nona Borka低，因此，初步认为这3种单倍型是耐盐单倍型。这些结果为培育水稻繁殖期耐盐品种提供优异的耐盐资源，基因和分子标记。