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Postharvest Pathology and Mycotoxins

Possible Mechanisms by Which Postharvest Calcium Treatment Reduces Decay in Apples. W. S. Conway, Agricultural Research Service, U.S. Department of Agriculture, Horticultural Science Institute, Horticultural Crops Quality Laboratory, BARC-West, Beltsville, MD 20705; C. E. Sams, Agricultural Research Service, U.S. Department of Agriculture, Horticultural Science Institute, Horticultural Crops Quality Laboratory, BARC-West, Beltsville, MD 20705. Phytopathology 74:208-210. Accepted for publication 29 August 1983. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1984. DOI: 10.1094/Phyto-74-208.

Golden Delicious apples were pressure-infiltrated (68.95 kPa) with 0, 2, 4, 6, or 8% solutions of CaCl₂ and stored at 0 C. Another lot of fruits was stored in low (1%) oxygen storage (0 C). After 6 mo of storage, both lots were wound-inoculated with Penicillium expansum and incubated for 7 days at 20 C. The fruits treated with 4, 6, or 8% CaCl₂ and the fruits kept in low O₂ were equally firm. However, whereas the area of decay was reduced by only about 15% in fruits kept in low O₂, fruits infiltrated with 4, 6, or 8% CaCl₂ solutions had more than 50% less decay than nontreated fruits. Fungal growth on media was not retarded when dehydrated PDA and PDB were amended with CaCl₂ to a concentration of calcium at least twice that encountered by the fungus in the fruit. There was no correlation between total phenolic compounds in the flesh and calcium concentration of the tissue. These results imply that the effect of calcium in reducing decay is indirect and may be due to the formation of cell wall components resistant to degradation by P. expansum.