Postharvest disease management of Alternaria spots on tomato fruit by Annona muricata fruit extracts

The aim of this study was to assess Annona muricata L. fruit extracts as an alternative to synthetic fungicide against Alternaria alternata (Fries) Keissler, the causative agent of black spots of tomato fruit. Antifungal activities of A. muricata pulp and seed extracts were tested both in vitro and in vivo. The seed extracts were more potent at inhibiting A. alternata than the pulp extracts. The in vitro assay showed maximum inhibition of radial mycelial growth of A. alternata (90%) by methanol seed extracts, at the highest concentration of 6%. Similarly, the in vivo assay showed marked reduction in lesion diameter (2.1 mm) and consequent disease inhibition (84%) on the tomato fruit treated with methanol seed extracts. Scanning electron microscopy showed that A. muricata extracts significantly damaged the morphology of hyphae and conidial structures. The FT-IR spectrum obtained from methanol extracts showed bands representing important bioactive compounds that possess antifungal activity. Based on our findings, Annona muricata fruit extracts can be further explored as a potential, excellent alternative approach to control the postharvest Alternaria spots of tomato fruit.