Effects of mouldy core and core rot on physiological and biochemical responses of apple fruit

BACKGROUND: Apple mouldy core (MC) and core rot (CR) are pathogenic disorders associated with the core region of fruits of susceptible varieties that have open calyx tubes. MC is not economically important because its symptoms are restricted to within the seed cavities, but CR is an important postharvest disease because its symptoms penetrate the fruit flesh and bring about economic losses. Recently, most studies have focused on causal agents and control of apple MC and CR. However, there is little information on the physiological and biochemical responses of apple fruits with MC and CR. RESULTS: The results indicated that MC and CR have different effects on the physiological and biochemical indices of apple fruits. Higher polyphenol oxidase (PPO) activity and total phenolic content were found in MC, dry CR (DCR) and asymptomatic tissue of wet CR (asympWCR) fruits than in healthy fruits, as well as significantly higher catalase and peroxidase activities in DCR and symptomatic tissue of WCR (sympWCR) fruits respectively, while asympWCR fruits showed a marked increase in malondialdehyde content, membrane permeability and superoxide production and a significant decrease in superoxide dismutase activity. CONCLUSION: The findings suggest that PPO and phenolic compounds may play a key role in the defence system of apple fruits against MC and CR. (C) 2011 Society of Chemical Industry