Abstract
In 1991-2006, the protein content (PC) and amylose content (AC) of nonglutinous rice, variety Kirara 397, were examined in 15 areas, and the growth characteristics were examined in each area to clarify the factors causing yearly and regional differences. The range of the yearly (regional) variation on the average of all areas (years) was July 29th-Aug. 16 (July 29th-Aug. 9) in heading date, 5.0-61.0 (8.9-21.5)% in sterility, 21.1-23.5 (22.0-23.3)g in 1000-kernel-weight, 205-576 (398-593)kg/10a in grain yield, 7.2-8.6 (7.2-8.2)% in PC, and 18.3-22.2 (19.8-21.2)% in AC. The coefficient of yearly variation in each growth characteristics was 1.4-3.2 times, larger than that of regional variation. Among years, the earlier the heading date, the higher the temperature during the sensitive stage to stelile-type cool injury; the lower the sterility, the heavier the 1000-kernel-weight; and, the higher the grain yield, the lower was the PC. At 843-849°C of the cumulative daily mean temperature during 40 days after heading (CTAH), the PC were lowest. The regional variation of PC did not correlate with these growth characteristics, but the lower the ratio of peat soil in the paddy field and the lower the wind speed during tillering, the lower was the PC. On the other hand among both years and regions the higher the CTAH, especially among years the earlier the heading date, the lower was the AC. From those results, some guides to cultivation method of good-eating quality rice were clarified.
