High-yielding rice cultivars in Japan
1989
Nishiyama, I. (Tropical Agricultural Research Center, Owashi, Tsukuba, Ibaraki (Japan))
The super high-yielding rice project was initiated in Japan in 1981. In the studies of the physiological characteristics of different varieties, it was found that 1) Japonica varieties grown in high-yielding trials in northern Japan yielded approximately the same as indica varieties grown in southern Japan; 2) Korean indica-japonica crosses and the newly released Akenohoshi variety produced a large number of spikelets without exhibiting excessive growth; 3) Withering occurred in rice plants containing smaller amounts of carbohydrates in the culms and leaf sheaths; 4) Treatment with growth regulators improved Akenohoshi plant type and resulted in higher yields; 5) Analysis of carbohydrate content indicated that three aspects should be considered in breeding super high-yielding varieties-accumulation of carbohydrates at heading, dry matter production during ripening, and effective translocation to panicles; and 6) Studies on root morphology showed that the high-yielding indica and indica-japonica varieties have deeper root systems and higher ratio of the transectional
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