Abstract
Sterility was induced by low temperature at the booting stage in early maturing varieties in 1986, and in medium and late varieties in 1987, particularly in the varieties without cool tolerance at Hokkaid Agricultural Experiment Station, Sapporo. Eating quality also was greatly lowered in these varieties. The present study was conducted to clarify the relation between these two phenomena. Thirteen to 31 varieties grown in the paddy field and the cool water irrigation field were used in this experiment. Amylose and protein content of milled rice were measured. Eating quality was evaluated by a panel of fifteen members. Eating quality of the varieties with high sterility caused by low temperature in 1986 and 1987 was much lower than in the year with little damage by cool temperature at the booting stage. Protein contents of these varieties were much higher than that of the varieties with low sterility. When sterile spikelets were induced by low temperature stress in the cool water irrigation field, protein content of the varieties became higher, in proportion to the spikelet sterility. It was suggested that the main cause of lowering of eating quality found in the rice plants with high sterility was increases in protein content due to the increases in nitrogen translocation per fertile grain. Therefore, it is important to improve the cool tolerance at the booting stage in order to improve the eating quality of rice.
