Porat, R., Dept. Postharvest Sci. Fresh Produce, ARO, Volcani Center, Bet Dagan 50250, Israel
Lers, A., Dept. Postharvest Sci. Fresh Produce, ARO, Volcani Center, Bet Dagan 50250, Israel
Dori, S., Dept. Postharvest Sci. Fresh Produce, ARO, Volcani Center, Bet Dagan 50250, Israel
Cohen, L., Dept. Postharvest Sci. Fresh Produce, ARO, Volcani Center, Bet Dagan 50250, Israel
Weiss, B., Dept. Postharvest Sci. Fresh Produce, ARO, Volcani Center, Bet Dagan 50250, Israel
Daus, A., Dept. Postharvest Sci. Fresh Produce, ARO, Volcani Center, Bet Dagan 50250, Israel
Wilson, C.L., USDA-ARS, Appalachian Fruit Research Station, Kearneysville, WV 25430, United States
Droby, S., Dept. Postharvest Sci. Fresh Produce, ARO, Volcani Center, Bet Dagan 50250, Israel

UV irradiation enhanced the resistance of grapefruit against the development of green mold decay caused by Penicillium digitatum, the main postharvest pathogen of citrus fruit, and significantly inhibited the fungus' growth at the fruit wound sites. Immunoblotting analysis using specific citrus chitinase and β-1,3-endoglucanase antibodies, showed that UV irradiation, wounding 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 the other hand, UV irradiation or wounding of the fruit alone was unable to induce the accumulation of 39 and 43 kD β-1,3-endoglucanase proteins, but the combination of the two treatments increased these protein levels. It is suggested that both chitinase and β-1,3-endoglucanase may play a role in the UV-induced resistance of grapefruit against P. digitatum.