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RESEARCH PRODUCT

Wound-induced responses in leaves of strawberry cultivars differing in susceptibility to spider mite

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Summary The effect of leaf detachment and wounding on the activities of oxidative enzymes and ethylene production was studied in strawberry (Fragaria × ananassa) cultivars, differing in susceptibility to the spider mite (Tetranychus urticae Koch.). Strawberry plants were cultivated during winter in two growth conditions - with and without overwintering, in greenhouse and laboratory, respectively. Polyphenol oxidase activity, peroxidase activity and catalase activity in strawberry leaves depended on the cultivar analysed, type of treatment (detachment or detachment and wounding), as well as on plant growth conditions. Activities of all analysed enzymes were higher in control plants grown in laboratory than in those grown in greenhouse. Cv. ‘Zephyr’, more resistant to T. urticae, had higher activity of wound-induced polyphenol oxidase and peroxidase only for plants grown in laboratory conditions. In contrast, wounding suppressed catalase activity in both cultivars in both growth conditions. Detached leaves of both susceptible cv. ‘Korona’ and partially resistant cv. ‘Zephyr’ plants grown in greenhouse, evolved comparable amounts of wound-induced ethylene with higher rate in cv. ‘Korona’. In contrast, partially resistant cv. ‘Zephyr’, grown in laboratory, had the rate of ethylene production up to 15-times that from leaves of susceptible cv. ‘Korona’. Additional wounding caused even more pronounced differences in ethylene production. The differences in ethylene production between the cultivars were due to leaf integrity because no differences in ethylene production were found from leaf discs between the two cultivars. It is suggested that unfavourable growth condition-modulated responses to leaf wounding reflect changes of putative antiherbivore defense reactions.