棉花陆海渐渗系纤维强度QTL（qFS-20-1）的精细定位及候选基因鉴定

Dissection of molecular mechanism of fiber strength formation is an important foundation for improving the cotton fiber quality. From the segregation populations constructed by superior chromosome segment introgression line (CSIL) MBI9915 (BC5F3:5) and its recurrent parent CCRI36, our research group identified one fiber strength-related QTL derived from Gossypium barbadense chromosome 20, namely as qFS-20-1, which could explain the maximum phenotypic variability of 9.13% and contain 86 candidate genes. Based on the aforesaid results, this study will utilize the homozygous plant of qFS-20-1 segment obtained from the offspring population BC8F2 and CCRI36 as parents to develop a BC9F2 population of 2000 plants. Combination with BSA-seq technology and RNA-seq results, we will develop the SSR, SNP and InDel markers in the candidate interval, and conduct the fine mapping by improving the density of the molecular markers in the genetic map. The candidate genes will be further confirmed by the re-sequencing data and correlation analysis method, of which the the primary function will be analyzed by constructing the over-expression vectors for the genetic transformation of cotton . The research results will lay the theoretical foundation for illuminating the generative mechanism of fiber development during the secondary wall thickening period, which is of great significance for for simultaneous improvement of cotton yield and fiber quality.

解析纤维强度形成的分子机制是棉花纤维品质改良的重要基础。前期，课题组利用优质陆海渐渗系MBI9915（BC5F3:5）和轮回亲本中棉所36构建分离群体，在BC6F2和BC6F2:3世代中定位到来源于海岛棉20号染色体的纤维强度QTL（qFS-20-1），解释9.13%的最大表型变异率，该区段有86个海岛棉候选基因。在此基础上，本项目利用BC8F2群体内含qFS-20-1的渐渗片段纯合单株和中棉所36构建2000个单株的BC9F2分离群体，结合BSA-seq技术和RNA-seq结果，明确候选区间；开发SSR、SNP、InDel等标记，加密遗传图谱，精细定位qFS-20-1相关基因；利用重测序数据和关联分析鉴别候选基因，构建过表达载体进行棉花转基因验证，分析候选基因功能，为阐明纤维发育次生壁加厚期的发生机理奠定基础，对实现同步改良棉花产量和纤维品质具有重要意义。

纤维强度是决定棉纤维品质的关键数量性状之一，因此解析纤维发育次生壁加厚期的发生分子机制对同步改良棉花产量和纤维品质具有重要实际意义。本研究以课题组前期鉴定的多环境稳定纤维强度相关QTLqFS-20-1为研究对象，首先对优异陆海渐渗系MBI9915和陆地棉CCRI36构建的BC7F2中纤维强度极端材料进行混池分组分析结合转录组测序（BSR-seq），在20号染色体上鉴别到3.99Mb的候选区间；其次，对BC7F3中纤维强度极端材料进行混池分组分析测序（BSA-seq），在20号染色体上鉴别到23.14Mb的候选区间；最后，在3423个单株的BC9F2群体中鉴别到685个交换单株且对纤维强度极端材料进行BSA-seq测序，在20号染色体上鉴别到1Mb的候选区间，结合不同世代分离群体的精细定位和RNA-seq差异表达基因的qRT-PCR结果确定2个纤维强度发育相关的候选基因，基因克隆、载体构建且遗传转化至拟南芥和棉花初步验证功能，为阐明纤维强度形成的遗传机理奠定基础，对选育和推广高产优质棉花新品种提供有用的信息。