Assessment of chitosan for inhibition of Colletotrichum sp. on tomatoes and grapes

The objective of this study was to evaluate the antifungal properties of chitosan and to assess its role in the protection of tomato and grape plants against Colletotrichum sp. isolated from infected tissues of Dracaena sanderiana. The isolate was tested in vitro using PDA amended with five concentrations of chitosan (0, 1, 1.5, 2, 2.5%). Chitosan significantly (P < 0.05) inhibited the radial growth of this fungus, with a marked effect at the three highest concentrations, after 7 d incubation. The effective concentration that reduced the radial growth to 50% (EC50) was 2.28%. Tomato fruits and single berries treated with aqueous solutions of 1.0 and 2.5% (w/v) chitosan were artificially inoculated with Colletotrichum sp. and incubated at 4 and 24 °C. Lesion diameters were recorded 7 and 10 d after inoculation. After 10 d at 24 °C, chitosan significantly (P < 0.05) reduced the lesion size of tomato fruits treated with 1.0 and 2.5%. Lesion diameter on pre-treated berries was also significantly reduced at 24 °C. However, no differences were observed between the chitosan concentrations and the corresponding controls at 4 °C; no lesions developed on berries at either 7 or 10 d after inoculation and although lesion size on tomato fruits was smaller for all treatments when stored at 4 °C, there were no treatment differences.