Identification of QTLs for Heat Tolerance at Flowering Stage in Rice

【Objective】To assess the genetic effect of quantitative trait loci (QTLs) conferring heat tolerance at flowering stage in rice.【Method】 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.【Result】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. 【Conclusion】 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.