陆地棉第7染色体产量与纤维品质性状QTL遗传解析

Cotton is a leading fiber crop, and it is important to make an extensive study of QTL controlling yield and fiber quality traits for cotton molecular breeding. Our previous study showed that the QTL controlling yield and fiber quality traits on chromosome 7 were stable in different environments in upland cotton (CCRI 35 × Yumian 1) F2 and recombianant inbred line opulations, and both CCRI 35 and Yumian 1 had favorable QTL alleles for different traits. To ravel the genetic relationship of QTL on chromosome 7, the present study establishes a fine mapping population with about 3000 individual plants from a cross between recombinant line RIL014 and CCRI 35. For RIL40, the QTL region derived from Yumian 1 and the other chromosome regions derived from CCRI 35. The SSR markers mapped on chromosome 7 in (CCRI 35 × Yumian 1) recombinant population, SSR designed from G. raimondii genome sequence which corresponds the QTL region, ET-ISJ, IT-ISJ, SRAP, and SSR designed from upland cotton BAC-ends sequences where the QTL located, are used to construct a saturated genetic map of QTL region. The yield and fiber quality identified from (RIL014 × Yumian 1) F2 individuals, F3 and F4 recombinant lines are used to physical-map QTL for yield and fiber quality traits into the contig with 3-5 BAC clones. The putative QTL candidate genes are confered according to the sequences of QTL anchored-BAC clones. Based on the tissue expression patterns of putative QTL candidate genes, the QTL candidate genes are confirmed and cloned.

棉花是首要的纤维作物,深入研究棉花产量、纤维品质QTL对棉花分子育种具有重要意义。项目组前期利用陆地棉（中棉所35×渝棉1号）F2和RIL群体，在第7染色体检测到环境稳定的产量、纤维品质QTL，并发现中棉所35和渝棉1号具不同性状QTL的有利等位基因。为弄清第7染色体产量、纤维品质QTL间的遗传关系，本研究选择第7染色体QTL区域来源渝棉1号的重组系RIL014与中棉所35杂交，建立（RIL014×中棉所35）F2大群体。利用（中棉所35×渝棉1号）RIL群体第7染色体图谱的SSR、QTL区域对应雷蒙地棉基因组SSR、ET-ISJ、IT-ISJ、SRAP和QTL区域标记筛选陆地棉BAC库阳性克隆末端SSR标记构建遗传图谱。以F2单株、F3和F4重组系的产量和品质鉴定结果物理定位QTL。随后全测序QTL所在BAC克隆，推测QTL初步候选基因。根据初步候选基因表达分析结果，确定并克隆候选基因。

棉花是世界上首要的天然纤维作物。棉花产量、纤维品质性状属复杂的数量性状，易受环境影响，传统育种改良进展缓慢。为了精细定位实验室前期利用（中棉所35号×渝棉1号）重组自交系群体初步定位到第7染色体上稳定的纤维品质性状QTL，本研究根据（中棉所35号×渝棉1号）RIL群体的标记基因型，选择第7染色体纤维品质性状QTL区域来源渝棉1号（其他第7染色体区域来源于中棉所35号）的株系RIL014，与中棉所35号杂交建立F2精细定位群体。根据雷蒙德氏棉和亚洲棉基因组序列设计SSR引物与第7染色体上原有的SSR标记，构建第7染色体纤维品质性状QTL区域内高密度遗传连锁图谱，将第7染色体纤维品质性状QTL精细定位到0.17cM 内（SWU8775和SWU8789），对应陆地棉A07染色体62.6kb，该区域包含四个注释基因。基因对比克隆和RT-qPCR分析表明，陆地棉第7染色体纤维品质性状QTL候选基因可能为编码富亮氨酸激酶家族蛋白的基因LRR RLK（Gh_A07G179）。研究结果将为陆地棉分子标记辅助选择育种和棉花纤维发育机制研究奠定基础。