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Jōetsu, Japan

Terao T.,Hokuriku Research Center | Chiba M.,Hokuriku Research Center | Hirose T.,Hokuriku Research Center
Japanese Journal of Crop Science | Year: 2010

A simple equipment that rises the panicle temperature of rice in the daytime was developed to screen the strains of rice that were tolerant to high temperatures during the ripening stage. High temperature stress at the ripening stage is the main cause of chalky grains and hence degrades the grain quality. Fitting a clear plastic film tube made with OHP film (3 M, PP2500) around the panicle increased the spikelet temperature by around 0. 8°C without any effect on leaf photosynthesis. Attaching a black rubber sponge with a 2 cm width and 5 mm thickness inside the tube further rised the temperature by more than 2°C. The higher the spikelet temperature, the higher was the percentages of chalky grains. Although a slight lowering of night temperature (about 0. 15°C) by setting this equipment was observed, its effect on the occurrence of chalky grains seemed to be negligible. Evaluation of standard cultivars with different high temperature ripening tolerance indicated that the result of evaluation by this method well matched that by other evaluation methods. This method makes it possible to evaluate high temperature tolerance with only a single plant, which consequently makes it possible to evaluate the tolerance of segregating populations, although progeny testing might be necessary. Accordingly, it might be useful for the genetic analysis of the high temperature tolerance.

Furuhata M.,Hokuriku Research Center | Chosa T.,Hokuriku Research Center | Matsumura O.,Hokuriku Research Center | Ohsumi A.,Hokuriku Research Center
Japanese Journal of Crop Science | Year: 2010

The emergence and establishment of germinated iron oxide-coated paddy rice seeds were examined in the field and in pots to establish a method for direct seeding culture of iron oxide-coated seeds using an air-assisted row seeder in a cold districts. In this study, we focused on the prewarming of coated seeds to shorten the time to seedling emergence and establishment of direct seeding of iron oxide-coated germinated seeds. The effect of seeder passage treatment after heat processing of coated seeds on seedling emergence and establishment and that of cold storage of coated seeds were examined. Direct seeding of iron-coated germinated seeds resulted in earlier seedling emergence and higher establishment rate and promoted early growth under low temperature conditions, suggesting that iron oxide-coated germinated seeds would perform well in cold areas such as Hokuriku region. However, iron oxide-coated germinated seeds, after prewarming were markedly damaged by seeder passage treatment and were rapidly deteriorated in germinability during low temperature storage. Overall, the introduction of prewarming of coated seeds into direct seeding culture of iron oxide-coated seeds was difficult.

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