Table 1_Characterizing the long-term variation in grain quality of super hybrid rice under the interactive effects of nitrogen and climate.docx

However, systematic knowledge of how its grain quality has evolved alongside genetic yield improvement, and how it responds to variety factors, nitrogen (N) management, and climatic conditions, remains limited. Two-year field experiments were conducted at two subtropical sites using three representative super hybrid rice varieties representing different breeding phases and grown under four N application rates.

In addition, historical grain quality data from all 136 super hybrid rice varieties released between 2005 and 2023 were analyzed to assess long-term trends associated with breeding progress. The historical analysis revealed that head rice rate increased by 0.25% per year, whereas chalky grain rate, chalkiness degree, and amylose content declined significantly over the same period. Consistent with these trends, field experiments showed that cultivars from more recent breeding phases exhibited higher head rice rates, lower chalkiness, and lower protein and amylose contents than earlier varieties.