Adaptability of Rice Varieties for Late Culture of Direct Seeding on Well-drained Paddy Field

摘要

This experiment was conducted to select adaptable varieties of rice for late culture of direct seeding on well-drained paddy field, to study mechanism of yield stability. Experiment was composed of 2 nitrogen applying methods and 10 varieties and local strains (early and middle maturing) from 1976 to 1980. Yielding ability and yield stability were investigated by FINLAY's regression method and EBERHALT's test of deviation from regression. Results obtained are summarized as follows: 1. FINLAY's regression coefficients between each environmental yield and averaged yield of all environments were significant among varieties and strains except Nipponbare, however deviations from regression were not significant in all varieties and strains (Table 3). 2. Regression coefficients of semi panicle number types and panicle number types were above 1.0, while those of medium types and semi panicle weight types were below 1.0. It is suggested that yield stability was related to plant type. 3. Yield stability was studied in relation to stability of some yield components. Yield stability was less affected to stability of number of panicles per unit area, number of spikelets per unit area, and 1000 grain weight. It was closely related to stability of percentage of ripened grain (Table 4). 4. Ooseto and Saikai No. 137 showed good performance for late culture of direct seeding.