Intermittent warming of peaches reduces chilling injury by enhancing ethylene production and enzymes mediated by ethylene

Peaches (Prunus persica 'Hermoza') were ripened at 20 degreesC after harvest and either stored at 0 degreesC for four weeks (control) to induce chilling injury or given intermittent warming (IW) on the twelfth day of storage (20 degreesC for 24 h) to alleviate chilling injury (CI). Continuously stored fruit from control developed woolliness, a Cl disorder, during ripening at 20 degreesC after cold storage while only a small percentage of IW fruit developed woolliness. CI fruit produced less ethylene during ripening after storage, and this inhibited ethylene production was closely tied with woolliness development. The IW treatment caused enhanced ethylene production in the fruit when returned to 0 degreesC and the ethylene remained higher than control fruit until the end of the storage period. IW also induced the messages for 1-aminocyclopropane-1-carboxylic acid oxidase (ACO) and 1-aminocyclopropane-1-carboxylic acid synthase (ACS) in the ethylene synthesis pathway. IW also elevated the mRNA of the cell wall degrading enzymes polygalacturonase (PG) and endo-1,4-gluconase (EGase). The mRNAs of the cell wall enzymes and the enzymes in the ethylene synthesis pathway remained higher even after 5 d at 0 degreesC following the IW treatment. It is suggested that IW maintained the fruit tissue capacity to ripen normally by preventing inhibition of the ethylene synthesis pathway which occurred in the control fruit after extended storage.