Influences of Pollination with Soft-X-Irradiated Pollen on Seed Formation, Fruit Set, and Fruit Quality in Persimmon

Abstract

Pollination with soft-X-irradiated pollen caused the disappearance of almost all complete seeds in harvested fruit, resulting in the transformation into empty seeds, in 7 persimmon cultivars: ‘Fuyu’, ‘Matsumoto-Wase-Fuyu’, ‘Izu’, ‘Taishuu’, ‘Maekawa-jiro’, ‘Saijo’, and ‘Zenjimaru’. Although the ovules that formed by pollination with irradiated pollen normally developed just as non-irradiated ones until 2 weeks after pollination, severe abnormality in endosperm tissue and the cessation of embryo development were observed at 4 weeks after pollination. Setting rates of fruit formed by pollination with irradiated pollen were not different from ones with non-irradiated pollen in ‘Saijo’, ‘Zenjimaru’, or ‘Matsumoto-Wase-Fuyu’; a significant decline in the fruit setting rate occurred in ‘Taishuu’ pollinated with 1,000 Gy-irradiated pollen grains, and in ‘Fuyu’, ‘Maekawa-jiro’ and ‘Izu’ pollinated with 500 and 1,000 Gy-irradiated pollen grains. Pollination with irradiated pollen decreased the harvested fruit weight, width, and length in ‘Saijo’ and the length in ‘Fuyu’; in other cultivars, the fruit weight and size were not influenced on pollination with irradiated pollen. Regarding the juice Brix, flesh firmness, and rind color of harvested fruits, there were no significant differences between irradiated and non-irradiated pollination in any of the cultivars. Pollination with irradiated pollen reduced stylar-end cracking in ‘Maekawa-Jiro’ fruits, possibly resulting in the disappearance of large complete seeds. These results indicate that pollination with soft-X-irradiated pollen would be available for practical seedless or few seeded fruit production in persimmon.