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

The study of the interaction effects of climate, hybrid combination, and parents on rice quality can provide a scientific basis for further optimization of rice quality improvement strategies and improvement of rice disaster prevention and mitigation abilities. In 2021 and 2022, 15 hybrid combinations, obtained using three sterile lines and five restorer lines, were used as experimental materials under two ecological conditions (normal temperature in the early season and high temperature in the late season), and the responses of rice quality to hybrid combinations and their parents were investigated. The results showed that the differences in the eight rice qualities were all very significant (F value: 10.82^**–6723.28^**). The ratios 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% (P<0.05) higher than those in 2022, respectively, whereas the chalky rice rate was 37.91% (P<0.05) lower than that in 2022. The ratios of length to width and protein and head rice rates in the late season significantly increased by 3.96%, 7.34%, and 14.08% (P<0.05), respectively, compared to those in the early season. The chalky rice rate, gel consistency, and milled rice rate in the late season significantly decreased by 15.43%, 5.21%, and 1.85% (F value: 18.74^**–68.38^**) compared with those in the early season, respectively; however, there was no significant difference between chalkiness and amylose in the two seasons. The quality indices of the hybrid combinations prepared using different sterile lines and restorer lines were significantly different (F value: 3.01^*–69.32^**). The comprehensive quality of ‘Yexiang A’ in the hybrid combinations prepared by three sterile lines was relatively good. The comprehensive quality of ‘Luhui 127’ and ‘Luhui 276’ in the hybrid combination of the five restorer lines was relatively good. The variance of the special combining ability of parents for length-to-width ratio, chalkiness, chalky rice rate, protein, and amylose was very high (52.07%–92.39%), and the variance of general combining ability for gel consistency, milled rice rate, and head rice rate was very high (73.90%–86.20%). The broad sense heritability of eight quality indexes was high (48.29%–98.01%). There were significant or extremely significant differences in the ratio of length to width, chalky rice rate, protein, gel consistency, milled rice rate, and head rice rate between early season and late season (t value: 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 the chalkiness between the early and late seasons, there was a significant positive correlation between them (r value: 0.7614^**). In summary, the future breeding strategy for hybrid rice quality is to select restorer lines with low chalkiness, high gel consistency, head rice rate, and chalky rice rate, cross them with sterile lines with high length-to-width ratio, low chalkiness and chalky rice rate, approximately 8% protein content, and 16%–18% amylose content, and select high-quality hybrid rice varieties from the hybrid offspring.