低温要求量が少なく果実品質の優れるモモの育成
香川大学農学部（果樹園芸学研究室）では、冬季に芽が休眠から覚めるのに必要な低温要求量が極めて少ない亜熱帯起源のモモと食味品質が優れる日本のモモを相互に掛け合わせ、得られた実生から優良個体を選抜し、2014年に白肉品種の「KU-PP1」を、2016年に黄肉品種の「KU-PP2」を種苗登録しました。
これらの品種は、低温要求量が一般の品種と比べて大幅に少ないのが大きな特徴です。このため通常の品種に比べ、開花が２～３週間早まり、果実の成熟も前進することから、一般の極早生品種と同時期の６月上中旬に収穫できます。新品種は、開花が早いことで果実の生育期間が長くなり糖度が高くなります。また、新品種は収穫期が早いので、夏の夜蛾の被害や高温障害を受けにくい利点があります。さらに、休眠から覚めるのが早いため、早期加温のハウス促成栽培も可能であり、温暖化に伴う冬季の低温遭遇量の減少への適応も期待できます。
現在、岡山県や愛知県、千葉県の生産者により経済栽培や試験栽培が行われています。
Breeding of low-chill peach varieties with high eating quality
Laboratory of Fruit Crops, Faculty of Agriculture, Kagawa University registered the white-fleshed variety ‘KU-PP1’ in 2014 and the yellow-fleshed variety ‘KU-PP2’ in 2016. These were selected from the cross-seedlings between the peaches of subtropical origin, which have lower chilling requirement for breaking bud dormancy in winter, and Japanese high chilling peaches, which have excellent eating quality.
These varieties have much lower chilling requirements than ordinary varieties. This allows them to flower two to three weeks earlier than ordinary varieties and to ripen fruit earlier, resulting in harvest in mid-June, the same time as very early varieties. The new variety has a higher sugar content due to the earlier flowering and longer growing period of the fruit.
Fruit of these varieties harvested in early June are less susceptible to night moth damage and high temperature stress in summer. In addition, earlier release from bud dormancy of these varieties enables the early forcing culture in greenhouses, and adaptation to the conditions of warm winter due to global warming.
Currently, growers in Okayama, Aichi, and Chiba prefectures are conducting economic cultivation or test planting.