Evaluation of Screening Methods for Higher Seedling Establishment Rate of Direct Seeded Rice on the Soil Surface in Flooded Paddy Fields.

概要

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The correlation between the rate of seedling establishment (SE rate) of rice directly seeded on a medium with water and the percentage of the seedlings with a spiral seminal root (PSS) was examined. Brown rice was sown on a sterilized medium containing 0.2% (w/v) gellan gum with water 3 cm in depth, incubated in a growth chamber kept at 27°C under an illumination of 2.3 klx, and the PSS was determined. PSS values of standard varieties used for the classification of the root shape, Arroz da Terra (AR) with a high SE rate and Koshihikari (KS) with a low SE rate, were 72 and 10%, respectively. Among 76 varieties obtained from the IRRI Core Collection, KANIRANGA (KN) and CAWWA/FORTUNA 6-103-15 (CF) with PSS values of 100 and 96%, respectively, were selected and used for further experiments. The indices of spiral root growth of KN and CF were higher than those of AR and KS. The length of the seminal root in the zone from the seed and soil surface (R 1), which is one of the important parameters determining SE rate, was measured at the second leaf stage in a flooded water bath kept at 26, 28 and 30°C. R 1 of CF was significantly shorter than that of the other varieties, and R 1 of KN was similar to that of AR. We consider that the determination of PSS is a convenient and useful method for screening rice varieties with high SE rate for direct seeding in flooded paddy fields.
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