Significant losses of table grapes are seem during storage and marketing due mainly to the occurrence of gray mold (Botrytis cinerea Pers.:Fr.), whick has been frequently controlled by using sulfur dioxide (SO2). Due to increase in restrictions on the postharvest use of chemical products, considerable interest in alternative control measures has arise. The main objective of this study was to evaluate the effects of chitosan in 'Itália' grapes, aimed at post-harvest protection against B. cinerea. The direct and indirect effects of chitosan were evaluated in vivo by treating bunches of grapes before and after inoculation with the pathogen. Chitosan was used in the concentrations of 0.00; 0.25; 0.50; 1.00; 1.50 and 2.00 % (v/v). For inoculation, 10 grapes in each bunch were injured by piercing the grape to a depth of ±2 mm, followed spraying with B. cinerea conidia (± 10(5) conidia.mL-1). After the treatments, the bunches were kept at 25±1°C/80-90% RH. Disease incidence and severity evaluations were carried out daily. In vitro evaluations regarding the effect of the product were also carried out based upon mycelial growth and germination of B. cinerea conidia. When applied after inoculation with B. cinerea, 1.5 and 2.0 % (v/v) solutions of chitosan significantly reduced the occurrence of the disease, although when applied before inoculation there was no significant effect on the development of the disease. The higher concentrations of chitosan suppressed mycelial growth of the pathogen and delayed conidium germination.
Vitis vinifera L.; gray mold; induced resistance; control