Quantitative trait loci for high temperature tolerance in rice (Oryza sativa L.)

Dular, a rice variety that is tolerant to high temperature, usually has low yield potential and undesirable traits. Due to its diverse genetic background, however, Dular in combination with a high-yielding and improved rice variety such as NSIC Rc150 (Tubigan 9) which yields 8.5 t/ha, can produce new high genotypes with high yield potential and suitable for quantitative trait loci (QTL) analysis. To identify QTL of high-temperature tolerance in rice, the BC sub 2 F sub 4 lines derived from NSIC Rc 150 x Dular were grown in a glasshouse during the 2014 dry season. The temperature reached 39.88 deg C +- 0.17 (min. 29.84 +- 0.14) during heading and maturity stage. Pearson correlation and multiple linear regression analysis were used to evaluate phenotypic traits associated with fertility. Heading days, time of flowering, and dehiscent high-temperature were found to be associated with spikelet fertility. A total of 126 simple sequence repeat (SSR) DNA markers, spanning the 12 chromosomes in 3mb Bin system, were used in genotyping 246 progenies. QTLs were identified through inclusive composite interval mapping (ICIM) method using IciMapping 4.0 software. The six major QTLs detected for high-temperature tolerance were qHTfert3 with PVE of 57.4% (LOD 9.18) and qHTfert4 with PVE of 10.2% (LOD 8.46), qHTtof10 with PVE of 16.3% (LOD 9.95), qHtdht3 with PVE of 31.7% (LOD 7.83) and qHThd3 with PVE of 30.9% (LOD 6.54). Three minor QTLs were identified namely, qHTdht4 with PVE of 9.4% (LOD 8.15), qHTdht5 with PVE of 9.2% (LOD 7.18), qHTdht10 with PVE of 7.1% (LOD 6.69). Nine QTLs identified for high-temperature tolerance were located in chromosomes 1, 3, 4, 5 and 10. These findings can be used in rice breeding using marker-assisted selection (MAS) and fine mapping of novel genes for high-temperature tolerance.