Mapping quantitative trait loci for heat tolerance at anthesis in rice using chromosomal segment substitution lines

To study the genetic basis of heat tolerance at anthesis, a set of chromosome segment substitution lines (CSSLs) derived from Sasanishiki (japonica ssp. heat susceptible) and Habataki (indica spp. heat tolerant) were used for analysis across three high temperature environments. Spikelet fertility (SF), daily flowering time (DFT) and pollen shedding level (PSL) under high temperature (HT) were assessed. Eleven related QTLs were detected, of which, two QTLs qSFht2 and qSFht4.2 for spikelet fertility were identified on chromosomes 2 and 4. Four QTLs qDFT3, qDFT8, qDFT10.1 and qDFT11 for daily flowering time were detected on chromosomes 3, 8, 10 and 11. The other five QTLs qPSLht1, qPSLht4.1, qPSLht5, qPSLht7 and qPSLht10.2 on chromosomes 1, 4, 5, 7 and 10, respectively, were found had effects both on spikelet fertility and pollen shedding level. Of the 11 QTLs, 8 were overlapped with QTLs reported by others, 3 QTLs qPSLht4.1, qPSLht7 and qPSLht10.2 identified in this study were novel. The stability of qPSLht4.1 was further verified at different temperatures, which could be used to improve the pollen shedding and pollen growth on stigma for rice heat-tolerance breeding.