Abstract
We elucidated the correlation between temperature conditions and the brown rice quality of “Yamadanishiki,” a brewer’s rice cultivar. A strong correlation was observed between inspection grade and head brown rice yield ratio, with a tendency toward an increase in inspection grade with increased head brown rice yield ratio. The yield ratio of head brown rice with inspection grades of deluxe quality or higher was generally ≥85%. The inspection grade and head brown rice yield ratio were correlated with daily mean temperature during the grain-filling period, with a tendency toward a decline in inspection grade or head brown rice yield ratio at high temperatures. The correlation coefficient with daily mean temperature was particularly high during the mid-grain-filling period 11–20 days after heading. Daily mean temperatures during this period that resulted in inspection grades of deluxe quality or higher were ≤23.4°C for young seedlings and ≤24.1°C for seedlings in the mid-growth phase. The thousand-kernel weight was negatively correlated with the temperature 11–20 days after heading, and the percentage of milky white rice and white-back rice sharply increased when the daily mean temperature during this period was ≥26.5°C. A negative correlation was observed between protein concentration in brown rice; and white-back rice yield ratio and thus when the protein content of brown rice was high, the occurrence rate of white-back rice was lowered.
