Inhibition of postharvest decay in relation to induced disease resistance of strawberry fruit treated with high oxygen

Strawberry(Fragaria ananassa, Duch cv. FengXiang) fruits were stored in 60% O₂ or 100% O₂ or air(control) at 5℃ for up to 15 days following with one day shelf period in air at 20℃ to investigate the effects of high oxygen treatments on the decay control and its relation to the induction of disease resistance. Results indicate that the treatments with 60% O₂ or 100% O₂ significantly inhibit decay incidence, maintain higher levels of phenylalanine ammonium-lyase, polyphenol oxidase, chitinase and β-1,3-glucanase activities andtotal phenolic content during storage at 5℃. When the fruits are removed fromthe high oxygen atmospheres and hold for additional one day in air at 20℃, fruits treated with 60% O₂ or 100% O₂ also have significantly less decay rate and higher levels of phenylalanine ammonium-lyase and polyphenol oxidase activities and total phenolic content. 100% O₂ treatment is more effective in controlling fruit decay than 60% O₂ treatment. These results suggest that the inhibition of fruit decay by high oxygen treatment is related to the inductionof defensive enzyme activities. The induced disease resistance may be involved in the mechanisms by which high oxygen treatment can inhibit fruit decay in strawberry fruit.