STUDIES ON DRY-MATTER AND GRAIN PRODUCTION OF F1-HYBRID RICE IN CHINA .2. CHARACTERISTIC OF GRAIN PRODUCTION

In order to make clear the high yielding capacity of the F1 hybrid rice in China, the characteristics of grain production was examined by the yield components analysis and with reference to the source of contents accumulated to the grain during the ripening period with the same varieties used in the previous paper. It became obvious from the yield components analysis that there was a highly positive correlation between total number of spikelet per unit land area and brown rice yield (Fig. 1). High yield in the F1 hybrid rice was largely depended on spikelet number (ca. 40,000/m2) as compared with common rice varieties. The total number of spikelet in the F1 hybrid rice was due to increased spikelet number per one panicle rather than panicle number per one hill. The F1 hybrid rice showed comparatively high percentage of filled-spikelet (ca. 80%) in spite of its huge number of spikelet. This was caused by higher ratio of LAI to total number of spikelet (Source-Sink ratio) during the ripening period. Generally, brown rice yield is decided by the total amount of photosynthetic products, a carbohydrate stored in culm and leaf sheath before flowering, and of assimilate accumulated during the ripening period. In this experiment, the ratio of the storage translocated from the culm and leaf sheath to the spikelet was larger in the F1 hybrid than in common rice varieties. In addition, there was a highly positive correlation between translocated storage and brown rice yield (Fig. 4). This fact suggests that a comparatively high percentage of ripenedgrain in the F1 hybrid rice was attributed to the amount of storage. It can be concluded from the results mentioned above that high yield of F1 hybrid rice was realized by both factors: 1) remarkable large number of spikelet and 2) comparatively high percentage of ripened grain, which was attained by the high ratio of the storage translocated from the culm and leaf sheath and by high LAI during the ripening period. © 1990, CROP SCIENCE SOCIETY OF JAPAN. All rights reserved.