Investigation of the super high-yielding capacity from viewpoints of plant types and dry matter production of historical leading rice varieties in Japan
2015
Oka, M. | Okada, S. | Araki, T. | Sugimoto, H.
Varietal development has played a significant role in the increase of rice yield after Second World War in Japan. The study was conducted to clarify the super high-yielding capacity from viewpoints of plant types and dry matter production by using 4 historical leading rice varieties in warmer part of Japan. IR64, IRRI variety showing a panicle weight type was also included. There are two steps in the process of rice breeding for the purpose of high-yielding capacity. In the first step of the new ear-number type with short culms released from 1960s to 1990s, the lodging resistance was highly strengthen due to low plant height and ear number increased. The grain yield was higher in the new type of Hinohikari than in the old ear-weight type of Norin 18 with long culms, since the new type showed larger leaf area (source size) and large number of spikelets (sink size) at heading time (Table 3). In the second step of the super high-yielding varieties showing ear-weight type with shorter culms that has been released since 2000s, the type represented by Takanari and IR64 showed two interesting features of more large source and sink size, especially sink size compared with the new ear-number type (Fig. 2). As a result, the newly released varieties with large ear showed higher dry mater and grain productivities (Table 3), and the plant type representing the super high-yielding capacity is similar to the new super rice prototype that was proposed by IRRI (Khush, 1995).
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