Responses of rice qualities to temperature and light in three different ecological environments in karst regions

Rice cultivation in Karst regions shows significant variations in both yield and quality due to temperature and light. Herein, 241 varieties including 198 indica rice and 43 japonica rice were planted in three ecological regions to investigate responses of rice qualities to meteorological factors. Results showed that in regions with higher average temperature (25.43 °C) and less daily sunshine hour (2.53 h/day), the appearance qualities (chalkiness degree, chalkiness rate and size) and processing qualities (brown rice percentage, head rice and milled rice percentages) were significantly reduced (p < 0.05). A total of 723 samples in three ecological environments were grouped into 4 clusters, arranged in descending order of cluster scores. In high-scoring cluster, the processing quality, appearance quality, protein content, hot paste viscosity, consistence viscosity, and setback viscosity were negatively correlated with temperatures (average temperature, temperature difference, effective accumulated temperature, maximum and minimum temperatures) from heading to mature stages, but positively correlated with sunshine hours. Apparent amylose contents were negatively correlated with temperatures but not significantly correlated with sunshine hours. In low-scoring cluster, only the processing quality had significant correlations with meteorological factors. These findings revealed the interaction between temperature and light for the formation of rice quality.