Effect of combining MCP treatment, heat treatment, and biocontrol on the reduction of postharvest decay of 'Golden Delicious' apples

'Golden Delicious' apples were treated with 1-methyleyclopropene (MCP) or kept at room temperature for the duration of the MCP treatment. After the MCP treatment, they were wounded and inoculated with the pathogen Penicillium expansum or with P. eypansum and a heat tolerant yeast (antagonist). After incubation at room temperature for up to 48 h, the apples were treated with heat at 38 degreesC for 4 days, and/or moved to cold storage for up to 5 months. Heat had an eradicative effect, when the pathogen was allowed to incubate in the apple wounds for 6 or 12 h after inoculation, resulting in less decay than at any other incubation time. The highest decay incidence occurred on the control that was inoculated with the pathogen and placed in cold storage. The least decay incidence and the smallest lesion diameter occurred on apples treated with a combination of the antagonist plus heat or heat alone. In general, MCP-treated apples had a higher lesion incidence, but similar lesion severity compared with non-MCP-treated apples. Only in the combination treatment of heat plus the antagonist, when the incubation time of the pathogen was between 6 and 24 h, was the lesion diameter slightly larger on MCP-treated fruit than on fruit not treated with MCP. This difference between the MCP-treated apples and non-MCP-treated apples decreased during storage. Antagonist populations in the apple wounds were stable or increased for all treatments. They were higher on MCP-treated apples than on non-MCP-treated apples and they increased with increasing incubation periods at room temperature after inoculation. Antagonist populations on apples heat treated after inoculation were higher than those kept at room temperature immediately after the heat treatment and after 3 months storage. The heat treatment had an eradicative effect, whereas the antagonist had a protective effect. The combination of heat and antagonist was more effective than either treatment alone, even when there was a delay of the heat treatment for up to 24 h. The combination of these two control measures, therefore, was complementary and resulted in better decay control than either treatment alone. Published by Elsevier Science B.V.