'土佐文旦'におけるストレプトマイシン処理と摘果時期の違いが無核果実生産に及ぼす影響(栽培管理・作型)  [in Japanese] Effects of Streptomycin and Fruit Thinning Time on Seedless Fruit Production in 'Tosa Buntan' Pummelo(Crop Production & Cropping Type)  [in Japanese]

'土佐文旦'の無核果実の生産について検討するため,単植園栽培においてストレプトマイシン(SM)処理を行い,果実発育に有効な摘果時期を明らかにした.SM500ppm溶液を開花率1〜5%,50%および100%のときに動力噴霧器で樹全体に3回散布することにより,種子形成が抑制され,完全な無核果実が生産された.また,不受精胚珠長が2mm未満で食べやすく,じょうのうの分離が容易で剥ぎやすくなることが認められた.満開4週間後(6月6日)に葉果比120程度でSM処理樹の摘果を行った結果,最も商品性の高い3L級の果実が30%以上に達した.亜主枝当たりの着果数,果肉割合やクエン酸含量は慣行栽培の人工受粉果実とほぼ同様であった.これらのことから,単植園栽培においてストレプトマイシン3回処理と満開4週間後の早期摘果により,商品価値の高い'土佐文旦'の無核果実を生産できることが明らかとなった.

To realize seedless fruit production in 'Tosa Buntan' pummelo (Citrus grandis Osb.), the effects of streptomycin (SM) spraying, open pollination and fruit thinning time on seedless fruit set and development were investigated in a commercial orchard consisting almost entirely of a single cultivar. Three spray applications of 500ppm SM to whole trees at 1-5%, 50% and 100% flowering time produced completely seedless fruit. Seedless fruits were not only easy to eat due to the minimal length of unfertilized ovules, but also easy to separate segments due to an undeveloped core. Fruit thinning with a leaf/fruit ratio of 120 4 weeks after full bloom increased seedless fruit size and over 30% of seedless fruit were the most commercially desirable 3L size. The number of fruit set per secondary scaffold branch, the proportion of edible portions and citric acid concentration were similar to those of hand-pollinated control fruit. These findings demonstrate that three spray treatments of SM and early fruit thinning 4 weeks after full bloom in a single cultivar produced a desirable size of seedless fruits in 'Tosa Buntan' pummelo.