Evaluation Method for Threshability of Rice Varieties by Grasping the Panicle with Hand

Abstract

We investigated the number of panicles per plant and number of plants necessary to evaluate the threshability of Japanese rice cultivars by grasping the panicles, using seven varieties, three with hard, two with middle, one with easy, and one with very easy threshability. Each of the four evaluators tested 50 plants and grasped 1, 3 or 5 panicles each time. The rate of shedding per panicle was not influenced by hand size or the number of grains grasped each time. Therefore, we selected the rate of shedding as an index for evaluation of threshability. The correlation among each rate of shedding investigated by four evaluators was the highest when the evaluator grasped three panicles than one or five panicles. The number of test plants necessary to calculate the rate of shedding to allow for a margin of sampling error of 10% points at a 5% significance level, varied with the threshability. It was 41-46, 24-32 and 14-18 plants in the varieties with hard, middle and very easy threshability, respectively. Use of at least 45 plants was recommended to evaluate threshability of unknown varieties by the grasping test.