Induction of chitinase and beta-1,3-endoglucanase proteins by UV irradiation and wounding in grapefruit peel tissue

UV irradiation enhanced the resistance of grapefruit against the developmen t of green mold decay caused by Penicillium digitatum, the main postharvest pathogen of citrus fruit, and significantly inhibited the fungus' growth a t the fruit wound sites. Immunoblotting analysis using specific citrus chit inase and beta-1,3-endoglucanase antibodies, showed that UV irradiation, wo unding of the fruit, or a combination of these two treatments, induced the accumulation of a 25 kD chitinase protein in the fruit's peel tissue. On th e other hand, UV irradiation or wounding of the fruit alone was unable to i nduce the accumulation of 39 and 43 kD beta-1,3-endoglucanase proteins, but the combination of the two treatments increased these protein levels. It i s suggested that both chitinase and beta-1,3-endoglucanase may play a role in the UV-induced resistance of grapefruit against P. digitatum.