日本寒地北海道稻作极限地带糯米外观品质的年度间地区间差异及其产生因素

Variation of the Appearance Quality of Glutinous Rice Grains Among Years and Among Areas, and Its Occurrence Factors in the Coldest Region for Rice Cultivation in Hokkaido, Japan

在六个种植地区及四个年度调查了北海道最寒冷的稻作地带生产的糯米外观品质。在不同年度之间,障碍型冷害危险期的平均气温和抽穗后40天之间的日平均累计气温(灌浆气温)越高,使得秕粒比率越低,千粒重越重,产量越高,整粒比率越高,未熟粒、受害粒及着色粒比率越低,大米蛋白质含量越低,糙米白度和大米白度越高。而在不同地区之间,这些关系不是很明确。这是由于各生育期的气温、生育特性以及整粒、未熟粒比率的变动(最小值与最大值之差以及变异系数)其年度间要比地区间大。但是,受害粒和着色粒比率其变动年度间要比地区间小,年度和地区综合分析时当灌浆气温分别为845、857℃时为最低,显示二次回归的关系。另外,整粒比率在年度间和地区间变化,受害粒和着色粒只在年度间变化;这些指标越差,同一年度时的地区间、同一地区时的年度间的变异系数就越大。烘干后半透明的阴糯籽粒与乳白不透明的糯米籽粒之间,其蛋白质含量、淀粉含量、淀粉颗粒的大小、纯化淀粉的碘吸收曲线最大吸收波长、吸光度等理化特性以及年糕面胚的明度基本上没有差异,且年糕面胚物理特性的差异不大,因此混有阴糯籽粒的糯米并不影响年糕面胚加工。与粳稻花粉杂交的糯稻品种胚乳变成粳性的异粉籽粒,其秕粒发生较多;虽然粳稻和糯稻的田块距离越远秕粒发生就越少,但是隔离距离600 m时也有发生。北海道为了避免糯米品质下降,在远离粳稻品种的地区种植糯稻。

Appearance quality of glutinous rice grains produced in the six areas of cultivation in the coldest regions for rice cultivation in Hokkaido, Japan was investigated during four years. Among years, the higher the temperature during the stage sensitive to sterile-type cool injury, and the cumulative daily mean temperature during 40 days after heading(grain-filling temperature), the lower the sterility, the heavier the 1000-kernel-weight, the higher the grain yield, higher the percentage of whole grain, the lower the percentages of immature, damaged and colored grains, the lower was the protein content, and the higher was the whiteness of both brown rice and milled rice. On the other hand, the relationship among the 6 areas was not clear. This was because the range of the yearly variation(differences between the two extreme values and coefficients of variation) in the temperatures during the growth stages, the growth characteristics, and the percentages of both whole grain and immature grain were larger than the regional variations. However,the range of the yearly variation in the percentages of damaged grain and colored grain were smaller than the regional variations, and the percentages of damaged grain and colored grain were the lowest in the quadratic regression relationship, at the grain-filling temperature of 843 ℃ and 857 ℃, respectively, among the 6areas during the 4 years. In addition, the percentage of whole kernels varies between years and regions, and the affected kernels and colored kernels only change between years;the worse these characteristics, the the larger the coefficient of variation among years in the same area or among areas in the same year. Moreover,glutinous grains, called mihaze grains, that are translucent after drying, did not show clear differences in physicochemical characteristics such as contents of both protein and starch, size of starch granules, iodine absorption spectrum of prepared starch and lightness of rice-cake dough as compared with the opaque grains called haze, and did not show large differences in physical property of rice-cake dough. Therefore,contamination of mihaze grains is considered to have little effect on the processing quality of rice-cake dough. Xenia seeds of glutinous rice plants occurred by outcrossing with pollen of a non-glutinous variety,and were found more in rice plants with high sterility than those with low sterility. The longer the isolation distance from non-glutinous variety to glutinous rice plant;the lower was the Xenia seed rate. However,Xenia seeds were found even at an isolation distance of 600 m. Therefore, in Hokkaido, to avoid quality deterioration, glutinous rice varieties should be cultivated in a district distant apart from paddy fields of non-glutinous rice varieties.