Effect of pre-harvest chitosan sprays on post-harvest infection by Botrytis cinerea and quality of strawberry fruit

The effect of pre-harvest sprays of chitosan on post-harvest decay and quality of strawberries stored at 3 and 13 degrees C was investigated. Strawberry plants were sprayed with 2, 4 and 6 g l(-1), chitosan solutions as the fruit were turning red. A second spray was performed after 10 days. Fruit were picked 5 and 10 days after each spray. Harvested fruit from chitosan sprayed plants were challenged with Botrytis cinerea. Chitosan sprays significantly reduced post-harvest fungal rot and maintained the keeping quality of the fruit compared with control. The incidence of decay decreased with increased chitosan concentration and increased with storage period and temperature. The second spray of chitosan extended the protective effect against decay of fruit from subsequent picks. Fruit from chitosan sprayed plants were firmer and ripened at a slower rate as indicated by anthocyanin content and titratable acidity than berries from non-treated plants. Chitosan sprays were not phytotoxic at all the concentrations tested. Chitosan sprays at 6 g l(-1) concentration performed twice, 10 days apart, protected the fruit from decay and kept the fruit quality at an acceptable level throughout the storage period of 4 weeks in fruit stored at 3 degrees C. The protective effect of chitosan sprays was more pronounced for fruit from pick 1 than pick 2. Kinetic data on decay and ripening characteristics provided quantitative evidence that chitosan compensates for higher storage temperature and protects against deterioration of lower quality fruit from the second harvest. (C) 2000 Elsevier Science B.V. All rights reserved.