莲藕多分枝形成机理及功能基因发掘

Sacred lotus (Nelumbo nucifera Gaertn.) is a kind of special vegetable in China, and increased yield is an important goal of sacred lotus breeding. Flower lotus ‘20140424’ has one more lateral branch (the second lateral branch) located in the boundary zone that separates the main branch from another lateral branch (the first lateral branch), this phenotype is quite different from that of the normal sacred lotus resources. Multiple shoot branches have the potential to improve all the yields of rhizome lotus, seed lotus and flower lotus. ‘20140424’ has been separately crossed with four normal sacred lotus as male parent and F1 seeds have been obtained. In the present study, a segregating population (F1 or F2) needs to be developed and on the basis of the whole genome sequences, the following studies will be carried out: whole genome resequencing of DNA from two bulked populations will be used to rapidly map the loci and candidate genes in control of the second lateral branch; the characteristic of the second lateral branch in different development period will be analyzed by paraffin sections in order to determine the cytological basis and critical period of the genesis of the second lateral branch, furthermore, candidate genes should be validated in the critical period by qRT-PCR. These findings obtained above will be important for a better understanding of the molecular mechanisms underlying the second lateral branch and provide theoretical basis for genetic improvement of sacred lotus resources. ‘20140424’ can be used as a high yield material for sacred lotus breeding.

莲藕（Nelumbo nucifera Gaertn.）是我国特色蔬菜，增产是莲藕育种的一项重要目标。本团队前期发现花莲‘20140424’具有多分枝现象，在主枝和侧枝之间长出第三枝，与正常莲藕资源（只具有主枝和侧枝）明显不同。增加分枝数对藕莲、花莲及子莲均有重要作用，有望增加其产量。本项目前期已利用多分枝‘20140424’为父本，与4个正常分枝莲藕品种杂交，获得了F1代种子。本项目拟获得性状分离的F1或F2代，并以其为材料，在具有莲藕基因组草图的基础上开展以下研究：利用重测序BSA技术对控制莲藕多分枝的基因进行初步定位和分析；基于石蜡切片分析多分枝腋芽发育各时期特征和动态过程，确定多分枝发生的细胞学基础和关键时期，并在该时期对候选基因进行qRT-PCR验证。通过以上研究不仅丰富和加深了对莲藕多分枝形成机制的理解，还为莲藕高产种质的遗传改良提供理论基础和优良的基因资源，具有实际应用价值。

莲藕（Nelumbo nucifera Gaertn.）是我国特色蔬菜，增产是莲藕育种的一项重要目标。花莲‘20140424’具有多分枝现象，在主枝和侧枝之间长出第三枝，与正常莲藕资源（只具有主枝和侧枝）明显不同。增加分枝数对藕莲、花莲及子莲均有重要作用，有望增加其产量。本研究以正常分枝莲藕‘巨无霸’和多分枝花莲‘20140424’顶芽为材料，通过石蜡切片确定多分枝发生的细胞学基础；同时在‘巨无霸’和‘20140424’莲鞭生长过程中，观察多分枝发生情况，明确两份材料的多分枝表型差异程度。以 ‘巨无霸’为母本， ‘20140424’为父本，构建了含173个单株的F2遗传群体。对亲本及群体主藕上的叶片数、多分枝数/主藕上的叶片、多分枝长出的最小节位、多分枝节数、多分枝总长、多分枝主节粗和多分枝支数/藕总支数等７个多分枝相关性状进行了表型鉴定，利用重测序获得的SNP标记对亲本及F2单株进行基因分型，结合表型和基因型数据对相关性状进行了QTL定位和分析。结果表明：莲藕顶芽内存在一大一小两个混合芽，大的混合芽为主藕芽，小的混合芽为子藕芽，多分枝芽长在子藕芽内。 与‘巨无霸’相比，‘20140424’叶腋形成多分枝芽的概率更高，多分枝芽发育成多分枝的概率也更高。多分枝相关性状在F2群体中均呈连续分布状态，表明均为多基因控制的数量性状。６个多分枝相关性状共检测到８个QTL位点，分布在５条连锁群上，LOD值变幅为2-3，解释1.547％-15.317％的表型变异率。贡献率≥10的QTL位点仅有１个，占QTL位点总数12.5％。多分枝总长在LOD阈值降到2仍未定位到区间。多分枝支数/藕总支数在３号连锁群12.762-13.047区间内，共有76个基因，其中有４个基因可能与多分枝的形成有关。通过以上研究不仅丰富和加深了对莲藕多分枝形成机制的理解，还为莲藕高产种质的遗传改良提供理论基础和优良的基因资源，具有实际应用价值。

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