栽培稲

About 1244 varieties of cultivated rice, collected from the main rice growing countries in the world, degree of grain shedding character was determined according to two different standards. In one case, it was determined by percentage of number of naturally shedding grains during harvesting, drying, storing or transporting time to total number of grains per five panicles for each variety, and in the other, by parcentage of number of forced dropped grains to total number of grains on the same sample, where the force was added by rolling over Wagner's pot four times over the sample enveloped linnen cloth on the desk. Degree of grain shedding character was classified for convenience into five classes for both categories, that is, rare, little, medium, many, and heavy, by the following boundaries of percentage of dropped grains, 2, 6, 14, 26% in the former and 5, 11, 21, 31% in the latter. The results were compiled in tables 1, 2 and 3. As shown in table 1, in both categories the number of varieties corresponding to rare degree of grain shedding is most numerous and gradually decreases toward to heavy degree of grain shedding and percentages of number of varieties of each class are 38, 31, 18, 9 and 4 in the naturally shedded percentage and 41, 18, 27, 11 and 3 in the forced dropped percentage. Althogh high correlation was found in both shedding character, some exceptional cases were also found, where varieties which belong to rare class of naturally grain shedding character were found in the heavy or many classes of forced grain shedded percentage and vice versa. In tables 2 and 3 number of varieties and percentage of them corresponding to each class are presented for individual countries. We,can see in these tables that degree of grain shedding character shows clear geographical different iation, for example high percentage of classes of rare of little degree of grain shedding is found in high latitude regions, namely in Japan, Manchuria, Chosen and Italy and in low latitude districts there is none or rare of such classes and most of varieties came from such countries as India, South and Central China, Africa and Taiwan showed heavy or many percentage of grain shedding in both categories. The authors also discussed about this character from the genetical view point.