Chitosan Treatment for the Control of Postharvest Decay of Table Grapes, Strawberries and Sweet Cherries

摘要

Table grapes, strawberries and sweet cherries are perishable fruits and can be affected by different diseases, both in the field and even more during postharvest storage. The main decay is gray mold (caused by Botrytis cinerea), which infects all three firiit, and Rhizopus rot (induced by Rhizopus stolonifer), which attacks mainly strawberry, at times sweet cherries, and rarely table grapes. Moreover, sweet cherries can suffer heavy losses mainly by brown rot (due to Monilinia spp.), and to a lesserextent, by blue mold (caused by Penicillium expansum, at times this can infect table grapes and strawberries, too), Alternaria rot, and Cladosporium rot (induced by Alternaria alternata and Cladosporium spp., respectively). Table grapes, strawberries andsweet cherries are often cold stored at 0°C soon after harvest, to retain quality, delay senescence, and reduce decay development. In several countries the use of synthetic fungicides after harvest is not allowed or there is a very short list of approved active ingredients. Therefore, together with consumer demand for food free of pesticide residues, the use of alternative means to control postharvest decay of fruit has gained increasing interest. Among these, chitosan has been identified as having the properties of an ideal coating for fruit. Preharvest and postharvest chitosan treatments of table grapes, sfrawberries and sweet cherries reduce their decay in the field and during storage, with the best performance at the highest tested concentration(usually 1%). Chitosan-based commercial products are available, and they have shown the same effectiveness as the biopolymer dissolved in an acid solution. Chitosan has a double mechanism of action: it reduces the growth of decay causing ftmgi, and it induces resistance responses in host tissues. With this double effectiveness, chitosan can be considered as the first compound of a new class of plant protection products.