Sensitivity of Botrytis cinerea to chitosan and acibenzolar-S-methyl

BACKGROUND: The antifungal properties of chitosan and acibenzolar-S-methyl were evaluated to assess their potential for protecting grapes against Botrytis cinerea Pers.: Fr. isolated from Vitis vinifera L. The objectives were to determine the effects of these compounds on the in vitro development of B. cinerea and to assess their effectiveness at controlling grey mould on grapes stored at different temperatures. RESULTS: Both agents significantly inhibited the radial growth of this fungus species. The EC50 was 1.77 mg m L-1 for chitosan and 3.44 mg mL(-1) for acibenzolar-S-methyl. In addition, single grapes treated with aqueous solutions of chitosan (1.0 and 2.5 mg mL(-1)) and acibenzolar-S-methyl (1.0 and 3.0 mg mL(-1)) were inoculated with B. cinerea and incubated at both 4 and 24 degrees C. After 4 days at 24 degrees C, all the concentrations of chitosan and acibenzolar-S-methyl significantly reduced B. cinerea growth. However, at 4 degrees C, significant differences were only observed between chitosan at 2.5 mg mL(-1) and acibenzolar-S-methyl at both 1.0 and 3.0 mg mL(-1) and the corresponding controls. After 3 days at 24 degrees C, the greatest reduction in lesion size was obtained in grapes pretreated with acibenzolar-S-methyl at 3.0 mg mL(-1). Only the highest doses of these products significantly reduced the lesion diameters when grapes were stored for 3 days at 4 degrees C. CONCLUSIONS: Chitosan and acibenzolar-S-methyl could directly inhibit the growth of Botrytis cinerea in vitro and confer resistance on grapes against grey mould. Pretreatment with these compounds could be an alternative to traditional fungicides in post-harvest disease control in grapes. (C) 2010 Society of Chemical Industry