Responses of chitinases in kiwifruit to curing and to long-term storage

Endochitinase activity and total protein content increased in stem plugs of kiwifruit (Actinidia deliciosa var. deliciosa cv. Hayward (A. Chev.) C.F. Liang et A.R. Ferguson) that were free of disease symptoms and had been "cured" for 7 days at 20°C, immediately following harvest. Isoelectric focusing, enzyme-linked immunosorbent assay (ELISA), and Western blots were used to identify chitinase isoforms induced by this treatment. Curing did not induce new chitinase isoforms, but appeared to increase expression of an existing ≪30 kDa protein, with putative chitinase activity, since it bound to antibodies against sugar beet chitinase. Chitinase activity also increased significantly in response to prolonged storage (6 weeks at 0°C) and inoculation with the pathogen, Botrytis cinerea (Pers.).