'ゴールド二十世紀'果実の糖蓄積に及ぼす葉果比の影響(栽培管理・作型)  [in Japanese] Effect of Leaf-Fruits Ratio on Sugar Accumulation of Japanese Pear 'Gold Nijisseiki' Fruits(Crop Production & Cropping Type)  [in Japanese]

ニホンナシ'ゴールド二十世紀'の収穫前の糖度推定法および成熟期の糖蓄積に及ぼす葉果比の影響について調査した収穫1か月前から収穫までの期間における,携帯型糖度センサーによる樹上果実の精度推定は,測定日ごとに異なるバイアスが生じるものの,屈折式糖度計測定値とセンサー測定値の相関関係は高いことから,バイアスの調整により可能であった.'ゴールド二十世紀'の収穫前30日間の精度変化を5年間調査した結果,この期間中の糖度変化は1.4〜2.3度であることが明らかになり,収穫前における糖度予測の可能性が認められた,収穫1か月前に摘果により葉果比を変更し,その後の糖度変化を携帯型セソサーで調査した.糖度は,葉果比が高い処理区ほど高くなった.この傾向は,処理後2週間目から認められた.同じ首里密度で紅葉枚数を少なくした処理区では,糖度の上昇程度は少なく適切な葉果比の確保が高品質果実の生産には重要であることが示された.葉果比と精度の関係から検討した結果,精度11度以上の果実を得るための葉果比は35〜50と考えられた.

We estimated Brix values of Japanese pear 'Gold Nijisseiki' fruit on the tree using a portable non-destructive near infrared spectrometer to compare net Brix value of the fruit during the 30-day period before harvest at different fruit load. Although the bias (mean of difference between actual Brix value and non-destructively derived value) differed on each measurement day, the correlation between estimated and measured values was high. Therefore, estimated Brix value of tree fruit could be used to adapt a bias correction for each measurement time. The increase in Brix value during 30 days before harvest for 5 seasons ranged from 1.4% to 2.3%. Thus, we could predict Brix value of mature fruit using an estimated Brix value of the tree fruit 30 days before harvest. Fruit load was regulated to 4, 6, 8, and 10 fruit per one meter length of lateral branch 30 days before harvest, and then the changes in fruit Brix value were estimated using the described method until harvest. The lower fruit load resulted in the higher increase in Brix value from 2 weeks after treatment. Defoliated branches showed a lower increase in Brix value than control branches, even if they had the same fruit load. Therefore, we concluded that the leaf-fruit ratio affects sugar accumulation during maturation in Japanese pear fruit and that an appropriate ratio to produce fruit having adequate Brix value (greater than 11) was 35/50.