The role of salicylic acid in postharvest ripening of kiwifruit

During postharvest ripening and softening of kiwifruit (Actinidia deliciosa (A. Chev.) C.F. Liang and A.R. Ferguson cv. Bruno) at 20 °C, the levels of salicylic acid (SA) in fruit tissues declined. Concurrently, lipoxygenase (LOX) activity increased, and this was associated with climacteric ethylene release. In fruit stored at 0 °C with a reduced rate of softening, SA concentrations remained at relatively high levels. Application of acetylsalicylic acid (ASA) to ripening kiwifruit resulted in substantially higher SA levels than in control fruit. ASA treatment slowed down the increase in LOX activity and superoxide free radical production, and suppressed ACC synthase and ACC oxidase activities and biosynthesis of ethylene, and hence retarded the climacteric rise in ethylene production. Fruit ripening and senescence were also delayed. A close relationship was found to exist between change in SA levels in the fruit tissues and the extent of fruit ripening and softening.