Pre-storage chitosan-thyme oil coating control anthracnose in mango fruit

Abstract

Anthracnose caused by Colletotrichum gloeosporioides is a severe postharvest mango disease. Postharvest application of fungicides is necessary to effectively control this disease, however, many of these fungicides are not allowed in many countries. In this study we aimed to investigate the combined effect of 1% chitosan plus 400 μLL−1 thyme oil to control anthracnose and improve shelf life of mango fruit (cv. White Chaunsa). We found that 400 μL L-1 thyme oil can completely inhibit in vitro mycelial growth of the fungus C. gloeosporioides. However, the combined application of 1% chitosan plus 400 μL L−1 thyme oil was more effective than thyme oil (400 μL L-1) alone in controlling the disease in artificially inoculated mango fruit. Furthermore, this combined treatment significantly (P ≤ 0.05) decreased naturally occurring decay. A mechanism related to promotion of fruit resistance by stimulation of phenolic metabolism is suggested by elevated phenylalanine ammonia-lyase (PAL) and peroxidase (POD) activities as compared to both the control and the synthetic fungicide Prochloraz. In addition, retention of physicochemical properties such as titratable acidity, total soluble solids, firmness, weight loss, color, and higher scores for sensory perception confirmed the efficacy of the treatment. This study demonstrated that the application of 1% chitosan plus 400 μL L-1 thyme oil more effectively controlled mango anthracnose as compared to synthetic fungicide; however, the commercial efficacy of the treatment needs to be tested.