萝卜叶片干枯基因的定位

Molecular Mapping of Withered Leaf Gene in Radish

萝卜叶片过早干枯影响植株生长和肉质根的形成,限制萝卜高产潜力的发挥。研究萝卜叶片干枯性状的遗传规律及定位相关基因,对于探索萝卜叶片干枯的发生机理及其调控机制具有重要意义。以萝卜自交系‘pp12Q-4-2’和‘36-2’为亲本构建F2分离群体,对其叶片干枯性状进行调查和遗传分析,同时观测叶片干枯对肉质根根粗和质量的影响。采用BSA法,利用基于萝卜全基因组测序开发的SSR引物对叶片干枯基因进行初定位,对初定位区域采用标记逐步加密的策略得到最终定位结果,并进行遗传图谱构建。研究结果表明:萝卜叶片过早干枯的植株叶绿素含量下降、肉质根生长发育受阻;叶片干枯性状符合质量性状的遗传特点,由隐性单基因控制,正常叶片对干枯叶片表现为显性;通过基因定位,最终将控制叶片干枯的基因定位于萝卜第7号染色体的scaffold89_21520和scaffold89_21545两标记之间,它们之间的遗传距离为0.8 c M,物理距离为211.63 kb,该区域包括43个候选基因。

The withered leaf directly influences plant growth and taproot formation,and affects the high-yield production in radish（Raphanus sativus L.）. Therefore,genetic analysis and molecular mapping of radish withered leaf gene are crucial for the discovery of withered leaf trait happening and its regulatory mechanism. Two radish inbred lines,‘pp12Q-4-2＇and‘36-2＇,were used as parents for F2 population development. Taproot thickness and weight were measured to analyze the effects of withered leaf trait on radish taproot development on the F2 population. Genetic analysis and gene mapping of withered leaf gene were conducted. Bulk segregation analysis（BSA）was performed on the samples from withered leaves and normal leaves respectively using SSR markers designed based on radish whole genome sequencing for primary gene mapping. More SSR primers were developed for searching closer-linked markers in the primary mapping region of withered leaf gene,and the genetic mapping was drawn. The result showed that withered leaf resulted in chlorophyll content reduction and severely affected taproot growth and development in radish. Genetic analysis suggested that withered leaf trait was qualitative and controlled by a single recessive nuclear gene. Normal leaf was dominant to withered leaf. Finally,the withered leaf gene was mapped between two flanking markers saffold89_21520 and scaffold89_21545 on chromosome 7,with a genetic distance of 0.8 c M and a physical distance of 211.63 kb. The predicted region contains a total of 43 candidate genes.