Identification of QTLs for heat tolerance at flowering stage in rice

Chinese. 通过对水稻抽穗开花期耐热性的遗传研究，为水稻耐热种质资源的利用及分子标记辅助选择育种提供理论和实践依据。以2个籼稻品种T219(对高温敏感)和T226（耐高温）为亲本构建的202个株系的重组自交系(RILs)，利用人工气候室进行了2年的高温处理试验，对RILs在抽穗开花期的耐热性状进行了主效应QTL以及QTL上位性分析。利用181个在亲本间具有多态性的SSR标记，构建了覆盖水稻全基因组1 559.6 cM、标记间平均距离为8.3cM的遗传连锁图谱。2年共检测到7个抽穗开花期耐热性主效应QTL以及7对上位性QTL。2004和2005年分别检测到3个和4个QTL，共解释29%和37.3%的表型变异。其中，qHt2、qHt3、qHt8和qHt12的耐热等位基因来自T226，而qHt9a和qHt9b的耐热等位基因来源于T219。位于第1、2、4、11和12染色体上4对QTL间以及位于第2、3、4、7、8和9染色体上的3对QTL间分别存在互作效应。水稻抽穗开花期耐热性受多个具有加性效应的基因控制，基因的效应比较小，基因间还存在互作效应。位于第3染色体的RM570-RM148标记位点（qHt3）在2年中同时检测到，可用于水稻耐热性分子标记辅助选择育种。

English. To assess the genetic effect of quantitative trait loci (QTLs) conferring heat tolerance at flowering stage in rice. We have developed a set of novel population with 202 recombinant inbred lines (RIL) derived from a cross between 2 indica varieties, T226 (heat tolerant) and T219 (susceptible ), and then treated the RIL population under high temperature regimes in growth chamber during flowering stage in 2004 and 2005, respectively. Main QTLs and epistatic QTLs for heat tolerance at flowering stage were detected. A genetic map with a total length of 1 559.6 cM and an average marker interval of 8.3 cM was constructed using 181 SSR markers with polymorphism between the two parents. Seven main effect QTLs and 7 digenic interactions controlling heat tolerance during flowering time were detected in two-year experiments. In 2004 and 2005, 3 and 4 QTLs were detected, totally explaining 29 % and 37.3% of phenotypic variances respectively. The alleles for increasing the heat tolerance were derived from T226 at qHt2, qHt3, qHt8 and qHt12, and from T219 at qHt9a and qHt9b. At the same time, 4 pairs of epistatic effect QTLs on chromosomes 1, 2, 4, 11 and 12, and 3 pairs of epistatic effect QTLs on chromosomes 2, 3, 4, 7, 8 and 9 were also detected. QTLs for heat tolerance during flowering time in rice were controlled by some main-effect with minor effects, and involved in epistatic interactions. The marker RM570-RM148 can be used in marker-assistant-selected method in heat tolerance breeding in rice.