Effects of chitosan in the control of postharvest anthracnose of soursop (Annona muricata) Fruit

The disease reducing activity of eco-friendly chitosan (molecular weight: 250 kDa, % deacetylation: 75-85, Sigma-Aldrich, MO, USA) compound against postharvest anthracnose caused by Colletotrichum gloeosporioides was investigated in in vitro and in vivo conditions. In this study, C. gloeosporioides was isolated in pure culture from soursop (Annona muricata) tropical fruit, identified by morphological and molecular methods and then used in experimental tools. In the in vitro tests, the inhibition of C. gloeosporioides mycelial growth, sporulation and conidial germination by chitosan at different concentrations, 0, 0.1, 0.5, 1.0 and 1.5% was evaluated on potato dextrose agar. The application of 1.0 and 1.5% chitosan decreased mycelial growth and sporulation by 90%, and completely inhibited spore germination. The 1.0% of chitosan solution shown the best performance in vitro. In the in vivo tests, a coating of 1.0% chitosan was applied on artificially inoculated soursop fruits during evaluations carried out after 3, 6, and 9 days. Chitosan completely inhibited anthracnose and reduced weight loss of fruit. Quality parameters of fruit (pH, total soluble solids, firmness and titratable acidity) were not affected by chitosan application. Therefore, coatings with 1.0% chitosan can be recommended as on alternative treatment to the application of synthetic fungicides for keeping quality and controlling anthracnose of soursop during storage and shelf life.