水稲冷害の実際的研究 : 第20報 障害型不稔発生度の株間および穂間変異について

抄録

In regard to rice plants differing in the variety, cultural condition and growth year, investigations were carried out to clarify the variation among hills as well as among panicles in the degree of sterile damage caused by the low temperature during the formation and development of young panicles, and further to determine a necessary number of samples required to estimate an average sterility percentage of a given field on the basis of the latest statistics. Results obtained may be summarized as follows ; 1. There was an inversely proportional relation observed between the sterility degree of a whole field and the coefficient of variation (c.v.) of sterility index (sin^-1√(percent. of sterile grains)) among hills. And the regression equation holding true between the above two and another equation representing the relation between a necessary number of samples and the coefficient of variation of an item to be investigated made it possible to calculate the number of hills to be sampled in a given field according to the degree of damage, the level of significance and the precision of investigation. 2. The c.v. of the sterility index among panicles in a hill showed a tendency to decrease while the sterile damage of the whole field increased, but it did not fall below 20 % at the lowest. In the case of a hill being regarded as an investigation unit, therefore, it will be necessary, from a statistical viewpoint, to investigate the strility percentage of all the panicles in a hill. 3. Percentage of sterile grains of a panicle having the largest number of spikelets in a hill seemed to be lower than that of the whole hill when the damage was comparatively heavy, while higher when it was comparatively small. 4. The c.v. of the sterility index among panicles sample at random from the field did not fall below 20 % in any case. It was considered to be necessary therefore to sample more than 60 panicles to estimate an average sterility perceatage of a given field with a significance of 95 % and a precision of 5 %.