Effects of climate warming on rice quality in relation to hybrid combinations and their parents

The study of the interaction effect of climate, hybrid combination and parents on rice quality can provide scientific basis for further optimizing rice quality improvement strategy and improving rice disaster prevention and mitigation ability. In 2021 and 2022, 15 hybrid combinations prepared by 3 sterile lines and 5 restorer lines were used as experimental materials under two ecological conditions: normal temperature in early season and high temperature in late season, the response of rice quality to hybrid combinations and their parents was studied. The results showed that the differences of the eight rice qualities were all very significant(F value 10.82^**~6723.28^**). The ratio of length to width, chalkiness, protein, amylose, gel consistency, milled rice rate and head rice rate in 2021 were 8.41%, 99.36%, 13.76%, 2.54%, 125.12%, 11.92% and 144.00% higher than those in 2022, respectively, while the chalkiness grain rate was 60.08% lower than that in 2022. The ratio of length to width, protein and head rice rate in late season were significantly increased by 3.96%, 7.34% and 14.08% compared with early season, respectively. The chalkiness grain rate, gel consistency and milled rice rate in late season were significantly decreased by 18.25%, 5.50% and 1.88% (F value 18.74^**~68.38^**) compared with that in early season, respectively, while chalkiness and amylose had no significant difference between two seasons. The quality indexes of the hybrid combinations prepared by different sterile lines and different restorer lines were significantly different (F value 3.01^*~69.32^**). The comprehensive quality of ‘Coconut A’ in the hybrid combinations prepared by 3 sterile lines was relatively good. The comprehensive quality of ‘Luhui 127’ and ‘Luhui 276’ in the hybrid combination of 5 restorer lines was relatively good. The variance of special combining ability of parents for length to width ratio, chalkiness, chalkiness grain rate, protein and amylose was higher (52.07%~92.39%), and the variance of general combining ability for gel consistency, milled rice rate and head rice rate was higher (73.90%~86.20%). The generalized heritability of 8 quality indexes was high (48.29%~98.01%). There were significant or extremely significant differences in the ratio of length to width,chalkiness grain rate, protein, gel consistency, milled rice rate and head rice rate between early season and late season (T-test value of paired data 1.98^*~8.70^**), and there was a very significant positive correlation between early season and late season (r value 0.6070^**~0.9672^**). Although there was no significant difference in chalkiness between early and late seasons, there was a very significant positive correlation between the two seasons (r value 0.7614^**). To sum up, the future breeding strategy for hybrid rice quality is to select restorer lines with low chalkiness, high gel consistency, head rice rate and chalkiness grain rate, cross them with sterility lines with large length to width ratio, low chalkiness and chalkiness grain rate, about 8% protein and 16%~18% amylose, and select high-quality hybrid rice varieties from the hybrid offspring.