Inhibitory Effects of Pinching and Defoliation against Current Shoots on Flower Bud Formation in Japanese Pear

We investigated inhibitory effects of the formation of axillary flower buds by pinching and defoliation of current shoots on four different cultivars of Japanese pear(Pyrus pyrifolia(Burm. f.) Nakai), to save labor for disbudding on the main one-year shoot of the scaffold branch. In 'Housui', the average rate of axillary flower bud formation was normally 86-95% in 2002-2004, but by pinching one-third off the shoot 50-65 days after full bloom, the rate in treatment was reduced to 40-54%. Further, the secondary- growth of shoots was promoted by earlier pinching treatment, and the flower buds formation was more effectively inhibited by secondary growth. In 'Shinko', 'Kousui' and 'Shurei', the earlier pinching treatment caused the same results as 'Housui', which inhibited the formation of axillary flower buds. The bud formation was especially inhibited not only in the part showing second- ary growth but also in that showing first growth. The defoliation treatment 50-65 days after full bloom inhibited the formation of axillary flower buds in 'Shinko' only. Thus, these findings suggest that the earlier pinching and defoliation treatment of current shoots can be a technique to control flower number as the working period does not compete with the disbudding period.ニホンナシの主枝，亜主枝および側枝等の先端1年生枝部分の摘蕾作業軽減を目的として，新梢に対する摘心と病葉による腋花芽着生の抑制効果を検討した．‘豊水’では，無処理区の腋花芽率が86～95%（3年間）であったが，満開50～65日後に新梢の先端1/3を摘心することにより腋花芽率は40～54%に抑制された．また，摘心の処理時期が早いほど，そして新梢の2次伸長部分が長いほど，抑制効果は大きかった．‘新興’，‘幸水’，および‘秋麗’においても，摘心は腋花芽着生を抑制した．摘心による腋花芽率の低下は2次伸長部分だけではなく，1次伸長部分においても認められた．新梢の基部から2/3の部分に対する機業は‘新興’において満開50～65日後の早い時期の処理で腋花芽着生を抑制した．これらのことから，骨格枝先端等の新梢における摘心と検量 は，摘蕾と作業時期が競合しない開花数調節の技術として有効と考えられた