Changes of Climatic Variables during Grain-filling Stage Affect Yield and Quality of Rice Cultivars Bred from Different Regions in Taiwan

Abstract

Changes in climatic variables during grain-filling stage are known to affect yield and quality of rice at harvest. However, there exist differential effects on cultivars that bred from varied regions with diversified genetic contexts and environmental conditions. To effectively response to different conditions emerging from changing climate for a stable food supply, it is necessary to further clarify the underlying mechanisms of climatic effects. This study was conducted in years from 2008 to 2010 with a total of 29 cropping seasons based on 24 Solar Terms calendar. Four rice (Oryza sativa L.) cultivars bred from different regions in Taiwan were selected for experiments, and weather data recorded from nearby meteorological station were used for analyses. The mean values of daily mean air temperature, daily maximum air temperature, daily minimum air temperature, day-night temperature difference, daily sunshine hours and daily irradiance during grain-filling stage were calculated as six climatic variables of MDMAT, MDMAXAT, MDMINAT, MDNTD, MDSH and MDIR, respectively. Results showed that temperature variables had a greater weight than irradiance and sunshine hour, and amylose, transparency and head rice rate of milled grains were the quality traits affected by temperature changes. The curvilinear relationships were significant only for 'TY4' in the first-half years (FHY), but were significant for all cultivars in the second-half years (SHY). Temperature variables also had an effect on grain yield, the convex curve patterns indicating that there were optimal temperature regimes. Analyses on the pooled data of 4 cultivars indicated that rice yields reached the plateau at MDMINAT of 23℃, MDMAT of 26.5℃ and MDMAXAT of 31℃ in FHY, and were at MDMINAT of 20℃, MDMAT of 24℃ and MDMAXAT of 29℃ in SHY. Both MDNTD and MDIR had a quadratic relationship with quality traits in SHY, and similar relationship was found in MDNTD with grain yield in SHY. This study demonstrated the differential effects of climatic variables during grain-filling stage on chemical components, physical characters and yield of rice grains in cultivars bred from varied regions. Temperature variables above the threshold values that obtained the maximum yield result in a decline of yield production.