QTL for Rice Heat Tolerance in Different Genetic Backgrounds

Climate change has resulted in the more frequent occurrence of heat waves that has negatively affected crop production. Yield reduction due to heat stress in rice has been reported in countries of Asia, Africa and the Americas. Developing varieties that can tolerate heat stress has been hampered by the poor understanding of the genetics of rice heat tolerance.

To identify quantitative trail loci (QTL) underlying heat tolerance in different genetic backgrounds, we crossed IR64 (susceptible) and Milyang23 (moderate tolerant) with Giza178 (tolerant) to develop two F2 populations. The IR64/Giza178 and Milyang23/Giza178 progenies were exposed to day/night temperature of 38/24 °C for 14 days at flowering stage, and genotyped by Illumina BeadXpress 384-plex SNP assay. To validate identified QTL, tolerant plants from Milyang23/Giza178 were crossed with IR64 and F2 plants of IR64//Milyang23/Giza178 were phenotyped under the same high temperature conditions and genotyped using Infinium 6K SNP assay.

Four QTL were identified in the IR64/Giza178 population, and 2 other QTL were identified in the Milyang23/Giza178 population. The QTL on chromosome 4 (qHTSF4.1) was located in the same region of a QTL we reported previously in an IR64/N22 population. Five QTL were validated using the three-way-cross population and high density SNP genotyping. The results from different populations revealed that heat tolerance in rice at flowering stage is mostly controlled by many genes with small effects. QTL qHTSF4.1 was consistent across different genetic backgrounds and could be an important donor for improving heat tolerance in rice via marker assisted breeding.