Pooled Mapping of Quantitative Trait Loci Conferring Heat Tolerance at Seedling Stage in Rice (Oryza sativa L.)

Global warming threatens human life on many aspects, including heat stress on crop production. Breeding heat-tolerant varieties is a fundamental way to meet the challenge. To study the genetic basis of seedling tolerance to heat stress in rice (Oryza sativa L.), we performed QTL mapping based on a large F2 population consisting of 4450 individuals derived from a cross between a japonica rice variety Huaidao 5 (HD5) and an indica rice variety 1892S using the method of bulked segregant analysis coupled with whole-genome sequencing (BSA-seq). HD5 was more tolerant to high temperature than 1892S at the seedling stage. By analyzing a pair of opposite DNA pools made from 124 extremely-sensitive seedlings and 178 extremely-tolerant seedlings from the F2 population using the block regression mapping (BRM) method, we mapped a QTL on chromosome 12, of which the additive effect was estimated to explain 3.75% of the phenotypic variance. We named the QTL qSLHT12.1, which must be a novel QTL, because no QTLs for rice seedling tolerance to heat stress have been mapped on chromosome 12 before. The information obtained in this study will facilitate marker-assisted breeding of heat-resistant lines and positional cloning of the gene conferring heat tolerance in rice.