Kochi Pref Agr Research Center

Nankoku, Japan

Kochi Pref Agr Research Center

Nankoku, Japan
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Takata S.,Kochi Pref Agr Research Center | Takata S.,Ehime University | Sakata M.,Kochi Pref Agr Research Center | Kameshima M.,Kochi Pref Agr Research Center | And 2 more authors.
Japanese Journal of Crop Science | Year: 2010

The factors relating to yearly and regional differences in the percentage of white immature kernels (WIK) were analyzed in Koshihikari and Natsuhikari cultured in the early-season in Kochi Prefecture. The percentage of WIK was consistently higher in Koshihikari than in Natsuhikari regardless of the year. The yearly difference in the percentage of WIK was larger in Koshihikari than in Natsuhikari. In Koshihikari, the percentage of white-based kernels (WBK) was high in the district where the daily minimum temperature at the early and middle stages of the ripening period (RP) was 23oC or higher, and the percentage of milky-white kernels (MWK) was high in the district where the daily sunshine hours at the middle stage of the RP were shorter than 6 hours. It was suggested that the yearly difference in the percentage of WIK was caused by the frequent occurrence of WBK in the year of higher daily minimum temperature at the early and middle stages of the RP and by the frequent occurrence of MWK in the year with shorter sunshine hours at the middle stage of the RP. In addition, marked regional differences in the percentage of WIK were observed regardless of the variety and the year, and it was closely associated with the growth state at heading as well as the meteorological conditions during the RP. In Koshihikari, it was suggested that the light manure application in the year of higher daily minimum temperature at the early and middle stages of the RP and heavy manure application in the year with lower sunshine hours at the middle stage of the RP tended to increase the percentages of WBK and MWK, respectively. On the other hand, in Natsuhikari the percentage of WIK tended to increase with increasing panicle length and the number of spikelets per m2 regardless of the meteorological condition during the RP.


Takata S.,Kochi Pref Agr Research Center | Takata S.,Ehime University | Sakata M.,Kochi Pref Agr Research Center | Kameshima M.,Kochi Pref Agr Research Center | And 2 more authors.
Japanese Journal of Crop Science | Year: 2010

Using 10 rice varieties cultured early in the year (early-season culture) in the warm south-western district of Japan, the type of white immature kernels that lowered husked rice quality in years with a high temperature and abundant sunshine (HTAS) and in years with a high temperature and poor sunshine (HTPS) was investigated. Whether the ripening capability (RC) under HTPS conditions could be evaluated by ripening the rice in a shaded (shading rate 66%) greenhouse was also examined. In the field examination, deterioration of husked rice quality was strongly related with the occurrence of white-back kernels and white-based kernels under the HTAS conditions, and with the occurrence of white-back kernels, white-based kernels and milky-white kernels (MWK) under the HTPS conditions. This suggested that the examination of the percentage of white-back kernels, white-based kernels and MWK was suitable for evaluating the RC of rice under the HTPS conditions. The percentage of MWK in the field in a year with HTPS was significantly correlated with that in the shaded greenhouse in a year with HTAS, which suggested that the RC under the HTPS conditions could be evaluated by ripening the plants in a shaded greenhouse. In addition, it was indicated that Fusaotome, Akitakomachi and Hatsuboshi which are used as standard varieties for "strong", "middle" and "weak" RC under high temperature conditions, respectively, are also available as standard varieties under the HTPS conditions, Tosapika and Okiniiri in which the percentage of MWK was similar to that in Fusaotome and Hatsuboshi were also judged to be available as standard varieties for "strong" and "weak" RC, respectively, under the HTPS conditions.


Takata S.,Kochi Pref Agr Research Center | Takata S.,Ehime University | Sakata M.,Kochi Pref Agr Research Center | Kameshima M.,Kochi Pref Agr Research Center | And 2 more authors.
Japanese Journal of Crop Science | Year: 2010

The varietal difference in the effect of the amount of basal nitrogen application (BNA) on the occurrence of white immature kernels (WIK) was examined using 22 rice varieties and lines (simply called varieties here after) to clarify the effective amount of BNA for the selection of varieties with high husked rice quality under high temperature conditions during the ripening period (RP). In many varieties, white-based kernels (WBK) decreased with the increase in the amount of BNA and improving the state of nutrition during the RP, while milky-white kernels (MWK) increased with increasing number of spikelets per panicle and decreasing allocation of carbohydrates to each spikelet. Moreover, the increase rate of WIK with increasing the amount of BNA varied with the variety, i. e., the number of MWK greatly increased in Fusaotome and Nangokusodachi, that of WBK greatly decreased in Hitomebore and Koshihikari, and those of both MWK and WBK changed only slightly in Kouiku 69 and Hatajirushi with increasing the amount of BNA. In addition, the varieties that increased the number of MWK greatly with increasing the amount of BNA tended to show a great increase in the number of panicles and grains per m2, and decrease in 1000-grain weight and percentage of ripened grains with increasing the amount of BNA. Thus, the effect of the amount of BNA on the occurrence of WIK varied with the variety, and it was suggested that the varieties with high husked rice quality under a high temperature conditions during the RP should be selected by evaluating the percentage of WBK and MWK under a light and heavy application, respectively.

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