Screening for Spikelet Fertility and Validation of Heat Tolerance in a Large Rice Mutant Population

Abstract A total of 10 000 M 4 individuals in Jao Hom Nil (JHN) mutant population was treated with high temperature (40 °C to 45 °C) during the day time (6 h) from the booting to the harvesting stages, and ambient temperature (33 °C to 35 °C) was used as the control. The results of screening and yield trials found that the mutant line M9962 had a high spikelet fertility of 78% under heat stress. In addition, the other mutant lines, including M3181 and M7988, had a spikelet fertility of approximately 70%. However, the JHN wild type, Sin Lek, RD15 and RD33 had very low spikelet fertility of 34%, 14%, 9% and 4%, respectively. The lower spikelet fertility at an elevated temperature resulted in a dramatic decrease of filled grain and contributed to a loss in 100-grain weight. M9962 is a potential genetic stock for use in a heat tolerance breeding programme. In addition, spikelet fertility at high temperature was representative of heat tolerance and can be used as a screening trait for heat tolerance during the reproductive phase on a large scale.