Delay of Fruit Softening in Forcing-cultured 'Tonewase' Japanese Persimmon by Packaging in Perforated Polyethylene Bags

'Tonewase' is an early maturity strain selected from 'Hiratanenashi', an astringent Japanese persimmon cultivar. In some districts of Japan, 'Tonewase' has been grown under forcing-culture conditions, which often results in rapid softening during postharvest distribution. In this study, we elucidated that this softening is caused by water-stress-induced ethylene that can be suppressed by reducing water loss by using perforated polyethylene bags (PPB). With or without removal of astringency by treatment with elevated carbon dioxide (CTSD method), forcing-cultured 'Tonewase' fruit produced significant amounts of ethylene two days after harvest ; thereafter, most fruit softened rapidly. This softening was markedly suppressed by treating the fruit with 1-methylcyclopropene (MCP), an inhibitor of ethylene action, which suggests the involvement of ethylene in fruit softening. Packaging 'Tonewase' fruit in PPB ranging from 0.03% to 0.3% of the total film surface area reduced water loss, retarded the commencement of ethylene production and delayed fruit softening. Immature field-grown 'Hiratanenashi' fruit behaved similarly to the forcing-cultured 'Tonewase' fruit with respect to ethylene production, softening and response to MCP treatment and PPB, whereas mature fruit under the same storage conditions produced no ethylene and remained firm during postharvest.