Effects of High Temperature at Grain Filling Stage on Grain Quality and Gene Transcription in Heat-Sensitive Versus Heat-Tolerant Rice Cultivars

There are many factors affecting rice yield and quality during cultivation, including temperature, light, water, and fertilization, among which high temperature (HT) is one of the main factors affecting rice yield and quality. However, less is known about the effects and potential mechanisms of different durations of HT stress during the grain filling stage on grain quality. In this study, the differences in rice quality and starch rapid viscosity analyzer (RVA) characteristics of eight indica rice varieties under different high-temperature treatment times were studied by simulating high temperature in an artificial climate chamber. The prolonged duration of HT leads to an overall deterioration in the milling quality, appearance quality, and cooking quality of rice. The impact of HT duration on the starch RVA characteristics of rice is more complex and is mainly related to the varieties. Among them, the starch RVA characteristics of R313 were more stable. It is worth noting that there is a significant difference in the sensitivity of the appearance quality of 8XR274 and 5W0076 to HT duration, with 8XR272 being more sensitive and 5W0076 being the opposite. We selected these two varieties for transcriptome analysis after 14 days of HT treatment and found that the number of differentially expressed genes (DEGs) in 8XR274 was significantly less than that in 5W0076. The DEGs of 8XR274 were mainly enriched in pathways related to carbohydrates, while 5W0076 was mainly enriched in pathways related to photosynthesis. Our study provides a new perspective on the molecular response and related genes of different rice varieties under high temperature, as well as the high-quality rice breeding under high temperature.