Effect of 1-MCP on Postharvest Diseases of Apple

In recent years, 1-MCP has shown tremendous potential in maintaining fruit quality in apples during storage. Blue mold (Penicillium expansum) and gray mold (Botrytis cinerea) are two important postharvest diseases of apples. Intensive and exclusive use of benzimidazoles has caused selection of thiabendazole-resistant (TBZ^R) pathogens in most packinghouses in the U.S., British Columbia and Ontario, causing an increase in the incidence of postharvest decay. The objective of this study was to determine the effect of 1-MCP on postharvest decay caused by TBZ^R- P. expansum and B. cinerea.

During 2002-2003, fruit from four apple cultivars that had been treated with 1-MCP and stored either in air at 0-1° C (‘Cortland’ - 122 d; ‘Delicious’ – 90 d; ‘Gala’ – 100 d) or in CA at 2° C or 0-1° C (‘Empire’ - 128 d) were wounded and inoculated with either TBZ^S (P28-8AS) or TBZ^R (PS-1R) P. expansum, or TBZ^R Botrytis cinerea (BC-2). Following inoculation, fruit were incubated in a moist chamber and held at 4°C for 30 days for ‘Cortland’, ‘Gala’ and ‘Delicious’, and at 20°C for 6 days for ‘Empire’, after which time fruit were evaluated for decay. There was no significant difference in disease incidence between 1-MCP-treated and non-treated apples that had been wounded and inoculated with TBZ-sensitive or TBZ-resistant P. expansum or TBZ^R Botrytis cinerea.

However, in wounded non-inoculated ‘Empire’ apples variable natural decays were observed. With the exception of apples stored in air, a higher percentage of decays were observed in 1-MCP-treated apples than the apples not treated with 1-MCP. The apples treated with 1-MCP had a higher percentage of disease incidence of blue mold caused by TBZ-sensitive, TBZ-resistant P. expansum, and gray mold caused by TBZ^R B. cinerea than apples not treated with 1-MCP. Treatment with DPA and ReTain had no significant effect on the decays caused by TBZ-sensitive, TBZ-resistant P. expansum, and by TBZ^R B. cinerea. Also, there was no significant interaction between 1-MCP and ReTain, or 1-MCP and DPA on disease incidence. A second year study on the effect of 1-MCP on postharvest diseases of apples is in progress.