基于SSSLs的野生稻柱头外露率QTLs定位与聚合育种研究

Stigma exsertion of rice male sterile lines is a main factor affecting hybrid seed production both between male sterile line and restore line, and between CMS line and maintainer line. It is important to explore gens controlling high percent of stigma exsertion in Oryza genus, as well as clarify the genetic bases and utilization potential in hybrid rice breeding. A library of chromosomal single segment substitution lines (SSSLs) in rice（O. sativa）has been developed in our lab by using an elite variety HJX74 as a recipient, 6 species of AA-genome wild rices as donors. We have mapped 12 QTLs for higher percent of stigma exsertion from SSSLs of O.glumaepatula, and a new QTL qPES1-2 was delimited to a physical region of 300 kb, and we have developed the two-QTLs pyramiding lines and intermediate materials of multiple-QTLs pyramiding lines of the relative SSSLs. In this proposed project, based on our earlier-stage works, we intend to work on: (1) Continue identifing and mapping QTLs from SSSLs of the AA-genome wild rices and analysis the additive effects of the QTLs. (2) Fine mapping qPES1-2 by using a larger F2 population within a further delimited region. (3) Developing homozygous pyramiding lines with two, three and four QTLs through molecular marker-assist selection of the pyramiding intermediate materials, detecting the pyramiding effects of every pyramiding lines and analysis the interaction effect of the QTLs, as well as analysis the potential of the elite pyramiding lines for improving stigma exsertion of rice CMS lines. This study will be helpful to clarify the genetic bases of stigma exsertion in wild rices, and guide the breeding by design of stigma exsertion in rice male sterile lines.

不育系柱头外露率直接影响杂交稻繁制种产量，发掘高柱头外露率基因并弄清楚其遗传基础及分子育种的应用非常重要。本实验室构建了以优良品种HJX74为受体、AA组野生稻为供体的染色体单片段代换系（SSSLs）文库，从展颖野稻为供体的SSSLs定位了12个高柱头外露率QTLs，其中一个新QTL qPES1-2定位在1号染色体约300kb区间；构建了QTLs所在SSSLs的二片段聚合系及多片段中间材料。在此基础上，本项目拟开展以下研究：（1）继续从AA组其它野生稻的SSSLs定位柱头外露率QTLs，分析其遗传效应。(2)扩大F2作图群体精细定位qPES1-2，进一步缩小其候选区间。(3)利用分子标记辅助选择，获得纯合2-4片段聚合系，分析QTLs的聚合效应及其遗传互作关系，并探索在不育系柱头外露率改良中的可行性。基于本研究有助于阐明野生稻高柱头外露率的遗传基础及其在不育系柱头外露率性状分子育种上的应用前景。

野生稻具有高的柱头外露率，是发掘高柱头外露率基因的有利资源。本研究利用课题组前期构建的AA组野生稻单片段代换系（SSSLs）文库，鉴定了44个来自普通野生稻、南方野生稻、展颖野生稻及短舌野生稻的稳定表达的高柱头外露率QTLs，这些QTLs的遗传效应分布范围在14.50 - 41.25%，其增效等位基因均来自野生稻。其中12个QTLs为未见报道的新QTLs。其中利用展颖野生稻单片段代换系A143和B50在1号染色体分别鉴定到QTL qSER-1b和qSER1-3。我们利用A143和B50分别与受体亲本HJX74杂交构建了F2群体，利用2个小的F2群体进行遗传连锁分析，证明了qSER-1b和qSER1-3均存在于相应的代换片段上，连锁关系成立。随后，我们利用大的F2分离群体、加密标记，筛选交换株，获得了两个QTL定位的纯合次级单片段代换系各14个和19个，利用代换作图法，最终将qSER-1b精细定位在234.79 kb的物理区间，将qSER1-3精细定位在135.2 kb的物理区间。此外，利用展颖野生稻携带高柱头外露率QTLs的8个SSSLs构建了10个二片段聚合系及8个三片段聚合系，利用5个短舌野生稻的SSSLs构建了4个二片段聚合系，利用4个南方野生稻的SSSLs构建了3个二片段聚合系。通过多个季节分析了聚合系的QTL上位性效应及聚合效应，筛选出优良聚合系B6/B19（qSERb3-1/qSERb12-1）、B6/B11（qSERb3-1/qSERb6-1）、G6/G14（qSER1-3/qSER-5）及G2/G11/G14（qSER-1b/qSER-3a/qSER-5），其聚合效应均大于或接近50%，有利于提高水稻柱头外露率。我们还利用2-QTL及3-QTL聚合系，开展了转育三系杂交稻保持系及不育系的研究，目前已获得相应后代材料，研究还在进行中。同时，筛选到柱头显著增大的SSSLs多份，其中利用一份来自短舌野生稻的SSSLs精细定位了一个控制柱头毛刷长的QTL qSBPL6-1，位于46 kb 的物理区间。相关研究结果有助于阐明野生稻高柱头外露率的遗传基础及其育种利用的价值和可行途径。