应用染色体片段代换系精细定位棉花D11染色体纤维强度QTL QFS-D11-1

The results of QTL mapping based on a primary mapping population should be further refined for its real utilization in marker-assisted selection or map-based cloning. The primary mapping population contains 223 F2 plants of the cross between Gossypium.hirsutum L.×G.barbadense L, genetic standard line of Upland cotton TM-1 and new line of Sea Island cotton H102. In this study, a genetic linkage map with 556 SSR markers spanning a total length of 4965.6cM was constructed using software JoinMap3.0. Composite interval mapping of WinQTL Cartographer Version 2.5 was used to map QTLs conferring fiber quality of the F2:3 lines. QTL QFS-D11-1 conferring fiber strength was mapped between NAU2950 and NAU4855 on Chro.D11 with 23.4% contribution rate. The continuous backcross between H102 as the donor parent and TM-1 as the recurrent parent was carried out to develop chromosome segment substitution lines (CSILS) of the target QTL QFS-D11-1 based on primary mapping results. The advanced F2 populations will be developed through crossing the target CSILS (IL-D11-2 and IL-D11-3) and TM-1. Besides, we will develop new EST-SSR, SSCP and TRAP molecular markers together with the existing SSR primers. The advanced F2 populations and designed molecular markers will be used to fine map QFS-D11-1 by constructing the secondary linkage map. It is expected to fine map QFS-D11-1 in 1 cM and gain one or two pairs of markers linked with QFS-D11-1 closely. The results will provide a basis for marker assisted selection of QFS-D11-1 in plant breeding and lay a foundation for cloning QFS-D11-1 and reveal its function.

纤维强度是影响我国纺织业发展的重要因素。本项目前期研究以陆地棉遗传标准系TM-1和海岛棉新品系H102为亲本配制杂交组合，创建223个单株的F2群体，并检测到1个棉花纤维强度QTL QFS-D11-1位于棉花基因组D11染色体NAU2950和NAU4855之间，两个标记遗传距离分别为4.5cM和5.1cM，解释表型变异为23.4%。以TM-1为轮回亲本与H102连续回交，构建了包含QFS-D11-1位点的染色体片段代换系(CSIL)IL-D11-2和IL-D11-3。本研究拟利用CSIL与TM-1构建次级F2群体，结合表型性状进行精细定位。并将目标QTL两侧标记扩增序列和雷蒙德氏棉基因组序列进行比对，结合染色体步移和电子克隆技术，将QFS-D11-1精细定位在1cM的遗传范围以内，获得1～2个紧密连锁的分子标记，为分子标记辅助选择利用提供了依据，同时也为下一步图位克隆和功能解析奠定基础。

纤维强度是影响我国纺织业发展的重要因素，精细定位棉花纤维强度QTL即为纤维品质分子标记辅助选择育种提供依据，同时也为下一步图为克隆及功能解析奠定基础。本研究首先从遗传力、样本大小及标记密度等方面对QTL准确定位策略进行了计算机模拟研究，结果显示初定位群体样本容量为450以上，标记间重组率为0.056和0.078的标记密度有助于获得较准确QTL定位结果。随着遗传力水平的增加，QTL检测功效与QTL检测准确度均随之升高，QTL置信区间缩减。遗传力水平大于50%时，检测功效均大于95%，当遗传力水平为10%时，不同程序检测对QTL检测功效小于35%，因此在实际分子标记辅助选择应用中，建议所选QTL遗传力需大于10%（最好大于30%），否则QTL的检测准确性将大大降低。其次以陆地棉遗传标准系TM-1和海岛棉新品系H102为亲本配置杂交组合，构建223个F2单株的初级群体，初定位结果显示纤维强度QTL QFS-D11-1位于棉花基因组D11染色体标记NAU2950和NAU4855之间，解释表型变异为23.4%。本研究以TM-1为轮回亲本，通过连续回交，构建了包含QFS-D11-1位点的染色体片段代换系（CSIL）IL-D11-2和IL-D11-3。再以IL-D11-2和TM-1为亲本构建了包含1002个单株的次级F2分离群体，基于次级群体构建区段遗传连锁图谱，结合考察的F2表型性状数据，进行QTL定位分析，在新图谱上检测到控制纤维强度的QTLQFS-D11-1，QFS-D11-1被定位在NAU2110~NAU2950区间，峰值最高点LOD值为34.0，加性效应是5.4cN/tex，距离NAU2110 2.3 cM, 距离NAU2950 0.5 cM, 95%置信区间为9.5～13.0 cM, 置信距缩小为3.5 cM，精细定位结果QTLQFS-D11-1距离标记NAU2950仅0.5 cM，为该基因的分子标记辅助选择利用提供了依据，同时也为下一步图位克隆QFS-D11-1、揭示QFS-D11-1的功能打下基础。