Multi-year field evidence for minimum nighttime temperature thresholds in rice fatty acid composition during grain filling

Fat content shapes rice eating and nutritional quality, yet its climate response remains unclear. In this study, we combined six years of multisite field observations across nine provinces in southern China with an interpretable random forest model to identify drivers of rice fat. The model showed that the minimum nighttime temperature during grain filling (TMIN) was identified as the primary factor. Fat content increased with TMIN, whereas the unsaturated fatty acid index (IUFA) exhibited three distinct accumulation patterns and generally declined at higher TMIN. This pattern indicates a physiological tradeoff potentially linked to changes in energy metabolism and membrane stability of rice. Patterns were independently validated in 2024 field trials at 11 sites. Furthermore, projections indicate higher fat under warming but declining IUFA, especially in early- and mid-season rice. These results support climate-resilient cultivation, sustainability, and quality management of rice.