ariation and Its Occurrence Factors of the Appearance Quality of Nonglutinous Rice Grains Among Years and Among Regions, in Cold Region, Hokkaido in Japan

Appearance quality of rice grains, including percentages of whole, immature, damaged, colored and opaque grain, and whiteness of brown, milled rice were examined in 15 areas of Hokkaido during 1999—2006 (6～8 years). The range of the yearly variation in those appearance qualities was 1.5～6.4 times larger than that of regional variation. That was because the annual difference of average temperature and mature temperature (40 days after heading) in sensitive stage to stelile-type cool injury (SSC, 24 days before heading and 30 days after heading) is 3.0～3.7 times larger than that of regional difference, while the rate of non seed setting, the growth characteristics of 1000 grain weight and brown rice yield and the protein content of rice are 1.4～3.3 times higher than that of regional difference. Among years, the heavier the 1 000 grain weight,the higher the whole grain ratio, and the higher the whole grain ratio, the lower the protein content due to high yield. In addition, the higher the temperature in SSC, the lower the rate of non seed setting, the lower the protein content, and the higher the CSTH, the higher the whiteness of brown rice and milled rice. There was a positive correlation between the ratio of damaged grain and colored grain. The higher the CTAH was, the lower the ratio was before the CTAH reached 890 ℃ and 850 ℃. Moreover, the ratio of immature grains was the lowest at 808 ℃ and showed a quadratic correlation, especially the effect of the second half of 40 days is greater than that of the first half. The lack of sunshine also makes the immature grains more frequent,too. Among regions, although these relationships are still unclear compared with those among years, the ratio of dead rice trends to increase in areas with low gray soil ratio and high peat soil ratio. At the present, these cultivation techniques that can improve the appearance quality of rice grains are gradually developed, further are popularized and guided by farmers. At the present cultivation techniqures that improve those appearance quality of rice grains have been developed and have disseminated to farmers.