Strategy for Combining Heat Treatment, Calcium Infiltration, and Biological Control to Reduce Postharvest Decay of `Gala' Apples

in HortScience
Authors:
William S. ConwayHorticultural Crops Quality Laboratory, Beltsville Agricultural Research Center Agricultural Research Service, U.S. Department of Agriculture, Beltsville, MD 20705

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Wojciech J. JanisiewiczAppalachian Fruit Research Station, Agricultural Research Service, U.S. Department of Agriculture, 45 Wiltshire Road, Kearneysville, WV 25430

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Joshua D. KleinDepartment of Field Crops, ARO, The Volcani Center, Bet Dagan 50250, Israel

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Carl E. SamsDepartment of Plant and Soil Sciences, The University of Tennessee, Knoxville, TN 37901

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The viability of Penicillium expansum Link conidia in sporulating culture declined rapidly when exposed to 38 °C, and when conidia were exposed to 38 °C prior to inoculation of apple fruits (Malus ×domestica Borkh.), the resulting lesions were smaller than those on fruit inoculated with nonheated conidia. `Gala' apples were heated after harvest (38 °C for 4 days), pressure infiltrated with a 2% solution of CaCl2, or treated with the antagonist Pseudomonas syringae van Hall, alone or in combinations to reduce postharvest decay caused by Penicillium expansum. After up to 6 months in storage at 1 °C, no decay lesions developed on fruit that were heated after inoculation with P. expansum, or any combination of P. expansum, antagonist, or Ca. Parallel lots of heat-treated and nonheated fruit that were either infiltrated or not infiltrated with Ca were stored up to 6 months. They were then inoculated with P. expansum alone, or with the antagonist followed by P. expansum. Prior heat treatment did not influence lesion size. Calcium alone, the antagonist alone, and heat plus Ca all reduced the incidence of decay by ≈25%, whereas heat plus the antagonist reduced it by 70%. Calcium plus the antagonist or Ca plus the antagonist and heat reduced decay incidence by 89% and 91%, respectively. The integrated strategy of heat-treating fruit, followed by Ca infiltration and then treatment with an antagonist, may be a useful alternative to controlling postharvest decay with fungicides.

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