Abstract
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 500 ppm 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.
