Involvement of phenolic compounds in host resistance against Botrytis cinerea in leaves of the two commercially important kiwifruit (Actinidia chinensis and A. deliciosa) cultivars

Expression of phenolic compounds associated with constitutive and wound-induced resistance to Botrytis cinerea was studied in leaves of two kiwifruit cultivars, Actinidia chinensis `Hort16A' and A. deliciosa `Hayward'. Constitutive leaf resistance to B. cinerea was much greater in `Hort16A' than in `Hayward'. This resistance might be attributable, in part, to phenolic compounds, since phenolic extracts from non-induced `Hort16A' leaves were significantly more fungitoxic than those from `Hayward'. Fungitoxicity correlated positively with concentrations of three components in the phenolic fraction, one of which was identified as caffeic acid. Wounding and inoculation induced resistance in `Hayward', but not `Hort16A' leaves. Induction was accompanied by an increased concentration of a fourth component in the phenolic fraction, although this compound did not appear to be directly anti-fungal. This is the first study to examine the relationship between resistance against B. cinerea and phenolic compounds in leaves of the two main commercial kiwifruit cultivars, and results suggest that three phenolic compounds may contribute to constitutive resistance in `Hort16A'.