On the Degree of Grain Shedding of Japonika-Indica Hybrid Rice Bred in Korea

Abstract

In order to clear the degree of grain shedding of the Japonica-Indica hybrid rice varieties bred in Korea, the strength required to detach rice grain from its pedicel or rachilla was measured at harvest time with an unbonded strain gauge transducer and a null barancing recorder. Besides 32 varieties of the Japonica-Indica hybrid rice, 169 varieties of Japonica type rice including 55 native varieties, 59 improved ones and 55 introduced ones from Japan during about 1920 to 1940 were also tested. The results obtained were summarized as follows. 1. Highly positive correlation was observed between the breaking tensile and breaking bending strengths in both Japonica-Indica hybrid and Japonica type rice varieties. In the two kinds of strengths, the former was always smaller than the latter. 2. Regarding the recommended rice varieties at present time, the breaking tensile strength was from 84 to 188 g in the Japonica-Indica hybrid and from 195 to 245 g in the Japonica type rices. 3. Breaking tensile strength was generally larger in the primary branch of lower portion than that of upper portion of an ear in the Japonica type rice varieties, while any clear trend was not observed in the Japonica-Indica hybrid rice. 4. In the half or more of the native varieties which were grown until the 1920s, in those days rice grain was threshed by shattering on the earth or wooden whacking frame etc., the range of their breaking tensile strength was about the same as that of the Japonica-Indica hybrid rice.