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 qual ity of strawberries stored at 3 and 13 degrees C was investigated. Strawber ry plants were sprayed with 2, 4 and 6 g l(-1), chitosan solutions as the f ruit were turning red. A second spray was performed after 10 days. Fruit we re picked 5 and 10 days after each spray. Harvested fruit from chitosan spr ayed plants were challenged with Botrytis cinerea. Chitosan sprays signific antly reduced post-harvest fungal rot and maintained the keeping quality of the fruit compared with control. The incidence of decay decreased with inc reased chitosan concentration and increased with storage period and tempera ture. The second spray of chitosan extended the protective effect against d ecay of fruit from subsequent picks. Fruit from chitosan sprayed plants wer e firmer and ripened at a slower rate as indicated by anthocyanin content a nd 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 e ffect of chitosan sprays was more pronounced for fruit from pick 1 than pic k 2. Kinetic data on decay and ripening characteristics provided quantitati ve evidence that chitosan compensates for higher storage temperature and pr otects against deterioration of lower quality fruit from the second harvest . (C) 2000 Elsevier Science B.V. All rights reserved.