Combination of chitosan and salicylic acid to control postharvest green mold caused by Penicillium digitatum in grapefruit fruit

Green mold caused by Penicillium digitatum is critical diseases for grapefruit fruit. In this study, the alone or combined effects of chitosan and salicylic acid on the control of green mold decay in grapefruit fruits were investigated. The results showed that combination of chitosan with SA treatment provided a more effective control of green mold than alone applying chitosan or SA. chitosan plus SA significantly reduced lesion diameter, disease incidence, while the content of endogenous SA much higher than those in treatment alone or control fruit. The combined treatment enhanced the chitinase, β-1,3-glucanase, peroxidase, phenylalanine ammonia-lyase and polyphenoloxidase activities and stimulated the synthesis of total phenolic compounds content. Moreover, the applications of alone or combined did not impair fruit postharvest quality such as firmness, weight loss and TA, while increased ascorbic acid and total soluble solids contents in grapefruit fruits. These result suggest that the use of chitosan combined SA treatment was effective in activating disease resistance against green mold, and providing a longer storage life with acceptable postharvest quality in grapefruit fruit.