Identification of stably expressed QTL for heading date using reciprocal introgression line and recombinant inbred line populations in rice

Two sets of reciprocal introgression lines (ILs) and a population of recombinant inbred lines (RILs) derived from the cross between japonica cultivar Xiushui09 and indica breeding line IR2061-520-6-9 (abbreviated as IR2061) were used to identify QTL for heading date (HD). Phenotyping was conducted in Hainan Island for two winter seasons (2007 and 2009). Nine QTLs were detected in the ILs with Xiushui09 background (XS-ILs), and four of which were repeatedly mapped across 2 years. Five QTLs were identified in the ILs with IR2061 background (IR-ILs), and three of which were commonly detected in 2 years. All commonly detected QTL had the same direction of gene effect. Seven QTL for HD were identified in the RILs in 2009. Only three (25%) QTLs were commonly detected using all the three populations (XS-ILs, IR-ILs and RILs). The number of commonly identified QTLs among populations was related to degree of similarity of their genetic backgrounds, suggesting that the genetic background effect is important for detecting HD QTL. QHd7 and QHd10b stably expressed in different populations and across years thus would be exploited in rice breeding programme. Moreover, lines with both of QHd7 and QHd10b resulted in at least 3 days earlier than lines with only one of them QTL, showing evident pyramiding effect.

本研究以粳稻（japonica）品种秀水09与籼稻（indica）育种系IR2061-520-6-9（简称IR2061）杂交衍生的两套互回交导入系（reciprocal introgression lines, ILs）群体，以及一套重组自交系（recombinant inbred lines, RILs）群体为材料，开展水稻抽穗期（heading date, HD）相关数量性状位点（quantitative trait locus, QTL）的定位分析。表型鉴定于海南岛进行，覆盖2007年与2009年两个冬季种植季。在秀水09遗传背景的互回交导入系（XS-ILs）群体中，共检测到9个抽穗期QTL，其中4个可在两年试验中重复定位得到；在IR2061遗传背景的互回交导入系（IR-ILs）群体中，共鉴定到5个抽穗期QTL，其中3个可在两年试验中共同检出。所有共同检出的QTL均表现出一致的基因效应方向。2009年在重组自交系群体中共鉴定到7个抽穗期QTL。仅3个（占比25%）QTL可在全部三个群体（XS-ILs、IR-ILs与RILs）中共同被检测到。不同群体间共同鉴定到的QTL数量与其遗传背景的相似程度呈显著相关，这表明遗传背景效应对于抽穗期QTL的检测具有重要意义。QHd7与QHd10b可在不同群体与不同种植季中稳定表达，因此可应用于水稻育种实践。此外，同时携带QHd7与QHd10b的株系，其抽穗期较仅携带其中单个QTL的株系至少提早3天，呈现出显著的聚合育种效应。