Effects of chitosan hydrolysate on control of postharvest infection caused by Botrytis cinerea and physiological responses of wounded tomato fruit

Chitosan is considered an eco-friendly plant protection agent. Chitosan hydrolysate (CH) with an average molecular weight (MW) of the main fraction of 135 x 103 Da, with a deacetylation degree (DD) of 93 % is an unfractionated product of nitric acid hydrolysis of high molecular weight chitosan. The effect of the CH on gray mold caused by Botrytis cinerea in tomato fruit stored at 25 degrees C was investigated. Chitosan provided effective control of B. cinerea on tomato fruit. The CH treatment of wounded tomato fruit had a protective effect, reducing the percentage of infected fruit on the 7 d after treatment to 50 %, compared with untreated wounded fruit (69 %) and water-treated fruit (88 %). The protective effect of the CH in tomato fruit may be due to a direct fungitoxic action against the pathogen. It was found that the CH induced an immune response in tomato fruit via the accumulation of phenolic compounds. The level of phenolic compounds in the CH group was higher than in the untreated wound group from day 1 to 5, with a maximum reached on day 3 (113 mg-eq GA kg-1 ). No significant differences were found in the activities of peroxidase, phenylalanine ammonia lyase, polyphenol oxidase, beta- 1,3- glucanase and chitinase. Thus, the CH affects the processes occurring during fruit damage and contributes to the preservation of the consumer qualities of fruit.