Susceptibility to Botrytis cinerea, and curing‐induced responses of lytic enzymes and phenolics in fruit of two kiwifruit (Actinidia) cultivars

Abstract

Botrytis cinerea rot incidence, hydrolytic enzyme activities and phenolics were measured in Botrytis cinerea‐inoculated fruit of two kiwifruit cultivars, Actinidia deliciosa ’Hayward’ and A. chinensis ’Hort16A’, following the presence or absence of a curing treatment. Disease incidence was 2‐fold higher (though not significant) in ‘Hayward’ than in ‘Hort16A’, irrespective of curing. Expression of putative defence mechanisms (chitinase activity and antifungal phenolics, in particular a compound with a Rf value of 0.56) was also higher in ‘Hort16A’ than in ‘Hayward’ pericarp tissue. Together these results suggest that genotype resistance to B. cinerea is greater in ‘Hort16A’ than in ‘Hayward’ fruit, and that chitinases and phenolic compounds may be among the factors contributing to this resistance. Curing decreased rot incidence in ‘Hayward’ from 80% to 20% (a 4‐fold reduction), whereas in ‘Hort16A’ it was decreased from 40% to 20% (a 2‐fold reduction). In trials carried out over two seasons, this seemed to be associated with small increases in concentration of antifungal putative phenolic compounds in ‘Hayward’ pericarp tissue, especially the Rf 0.56 compound. Actinidia fruit resistance appears to be a complex and multi‐facetted phenomenon.