研究キーワード：　モモ，スモモ，オウトウ，結実生理，品種改良

１．低温要求量の少ないモモの育種と利用

日本で栽培されているモモ品種は，休眠打破に必要な低温要求量が大きく，早い時期からのハウス栽培が困難である．一方，亜熱帯地域で栽培されている少低温要求性品種は，果実品質に劣る．そこで，これらを交配して，低温要求量が少なく早生で果実品質の優れるモモの育種を行い，これまでに２品種（KU-PP1：白肉、KU-PP2：黄肉）を登録した．現在，これらの品種の促成栽培における有効な利用法について研究している．　　

２． 自家和合性のニホンスモモの育種

ニホンスモモはほとんどの品種が自家不和合性であるため，結実の確保には受粉樹の混植や人工授粉を必要とする．これまでに，自家不和合性に関わるS遺伝子を分析して，各品種のS遺伝子型を特定するとともに，一部の品種にみられる自家和合性に関わるS遺伝子を明らかにし，自家和合性個体の選抜DNAマーカーを作出した．このマーカーを利用して，自家和合性で果実品質の優れるスモモの育種を行っている．　

３． 甘果オウトウ（サクランボ）の結実安定化　

暖地で甘果オウトウを栽培すると，結実不良が生じやすく，栽培上大きな問題となっている．これまでに，人工気象室での実験により，胚珠の発育や内生植物ホルモンが結実性に関わっていることを明らかにした．現在，結実性を向上させるための栽培技術ついて研究を行っている．また，中国オウトウ（暖地オウトウ）や亜熱帯地域の甘果オウトウを利用して，結実性に優れる品種の育成にも取り組んでいる．

Research Area:　Horticulture　

Research Specialization:　Pomology

Name:　BEPPU，Kenji

Keywords：　peach, plum, cherry, reproductive physiology, breeding

１．Breeding and utilization of lower-chilling peach　

　Forcing culture of peach under plastics is intended to ensure early shipping of production aimed at obtaining a higher market value. Usually, peach growers start forcing after attaining 900 chilling hours required by the high-chill cultivars. For achieving earlier forcing, lower-chilling peach with a high tasting quality would be necessary. Therefore, we bred a new cultivar named ‘KU-PP1’ and ‘KU-PP2’ that contained these traits by crossing Japanese high-chill and introduced low-chill cultivars. Currently we investigate effective methods for forcing culture with these cultivars.　

２． Breeding of self-compatible Japanese plum

  Most commercial cultivars of Japanese plum are self-incompatible and cross-compatible cultivars need to be interplanted. Thus, information about S-haplotypes of each cultivar is important. We demonstrated that the S-RNase genes of Japanese plum could be amplified effectively by S-RNase gene-specific primers, and identified 14 different S-RNase genes. In addition, we revealed the involvement of the S^e-haplotype in self-compatibility in Japanese plum and developed the S^e-RNase gene-specific primer. Currently, we are breeding self-compatible Japanese plum  cultivars with good fruit quality.

３． Regulation of fruit set of sweet cherry in warm region

　Poor fruit set due to physiological fruit drop have become serious problems preventing stable production of sweet cherry in warm regions. Under controlled conditions, we demonstrated that the fruit set rate decreased markedly due to the rapid degeneration of the embryo sacs when the trees were exposed to high temperatures above 20℃, and that gibberellin may be involved in this phenomenon. We also found that extremely high temperature in summer reduced photosynthesis and cause early defoliation, which result in low fruit set rate in the following spring. We have developed several methods to improve fruit set in warm regions.