Antifungal activity of chitosan on two postharvest pathogens of strawberry fruits
1992
Effect of chitosan coating on decay of strawberry fruits held at 13 C was investigated. Strawberry fruits were inoculated with spore suspensions of Botrytis cinerea or Rhizopus stolonifer and subsequently coated with chitosan solutions (10 or 15 mg/ml). After 14 days of storage, decay caused by B. cinerea or R. stolonifer was markedly reduced by chitosan coating. Decay was not reduced further when the concentration of chitosan coating was increased from 10 to 15 mg/ml. Coating intact strawberries with chitosan did not stimulate chitinase, chitosanase, or beta-1,3-glucanase activities in the tissue as revealed by polyacrylamide gel assays. Chitosan, when applied on freshly cut strawberries, however, stimulated acidic chitinase activity. Chitosan was very effective in inhibiting spore germination, germ tube elongation, and radial growth of B. cinerea and R. stolonifer in culture. Furthermore, chitosan at a concentration greater than 1.5 mg/ml induced morphological changes in R. stolonifer. Mechanisms by which chitosan coating reduced the decay of strawberries appear to be related to its fungistatic property rather than to its ability to induce defense enzymes such as chitinase, chitosanase, and beta-1,3-glucanase.
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