積算温度によるブドウの芽の休眠完了予測

　This study was conducted to investigate the relationship between completion of dormancy of grapevine bud and temperature. Canes of ‘Kyoho’ and ‘Pione’ grapevines (Vitis labrusca×V. vinifera) grown in 7 vineyards with different temperature conditions, in Nagano, Northern Okayama, Yamanashi, Okayama, Okayama University, Fukuoka and Miyazaki, were collected at three different chilling exposures, December, January and February. These were then sent to Okayama University all at the same time. Cuttings with one bud were put into growth chambers kept at 25 or 30°C with 14 hours daylength, and budbreak in each cutting was surveyed at two day intervals for 60 days. Cumulative chilling hours (CCH) of exposure to below 7.2°C in each treatment time was largest in Nagano, followed in order by Northern Okayama, Yamanashi, Okayama, Okayama University, Fukuoka and Miyazaki. The CCH in Nagano was 2.5 to 4.8 times larger than in Miyazaki depending on the treatment time. The later the treatment time and the higher the temperature, the fewer were the number of days to first budbreak (NDFB) after treatment, irrespective of cultivar. A similar trend was observed in the number of days to 60% budbreak. In ‘Kyoho’ the NDFB was short in Nagano, Okayama University and Miyazaki, and longer in Okayama, Yamanashi and Fukuoka. In ‘Pione’ the NDFB was short in Fukuoka and Okayama University, and longer in Yamanashi and Okayama. The result was a weak negative correlation observed between CCH and NDFB in 4 of 7 vineyards. However, there was a strong positive correlation between NDFB and cumulative temperature (CT), a summation of temperature and hours of exposure to above 0°C from November 1 to treatment time and hours of exposure to 25 or 30°C from start of treatment to budbreak in each plot, in 6 vineyards excluding Miyazaki. The importance of estimating the completion of dormancy in grapevine bud based on CT is discussed.

ブドウの芽の休眠完了と温度との関係を調査するため，温度条件の異なる７園（中信農試，山梨果試，岡山農試，岡山農試北部支場，岡山大学，福岡農試および宮崎）で栽培されている‘巨峰’と‘ピオーネ’から低温遭遇量の異なる３時期（12月，１月，２月）に結果母枝を採取した．直ちに岡山大学に送り，１芽を持つ挿し穂に調整した後，25または30℃のインキュベーター（14時間日長）に入れ，２日間隔で60日間発芽を調査した．処理開始時の7.2℃以下の遭遇量は中信農試で最も多く，次いで岡山農試北部支場，山梨果試，岡山農試，岡山大学，福岡農試，宮崎の順で，中信農試と宮崎では処理時期により2.5～4.8倍の差があった．発芽所要日数は，両品種とも処理時期が遅いほど，また温度が高いほど少なく，60％発芽所要日数もほぼ同様の傾向であった．‘巨峰’の発芽所用日数は中信農試，岡山大学および宮崎で少ない一方，岡山農試，山梨果試および福岡農試で多く，また‘ピオーネ’では福岡農試と岡山大学で少なく，山梨果試と岡山農試で多かった．７園のうち４園で低温遭遇量と発芽所要日数との間に負の相関がみられたが，相関係数は低かった．一方，11月以降処理開始までの０℃以上の温度の積算値と処理開始から発芽までの25または30℃での積算値を合計した積算温度と発芽所要日数との間には１園を除き極めて高い正の相関が認められた．これらの結果を基に，積算温度によるブドウの休眠完了予測の可能性を考察した．