Evaluation of the fungicidal properties of plant extracts to reduce Rhizopus stolonifer of 'ciruela' fruit (Spondias purpurea L.) during storage

Rhizopus stolonifer is one of the main postharvest pathogens of 'ciruela' fruit (red mombin) (Spondias purpurea L.) during handling and storage. To evaluate the fungicidal potential of plants indigenous to the state of Morelos, Mexico, aqueous extracts of leaves or stems of 19 different plant species were tested against Rhizopus development in vitro and in vivo. Extracts were applied to fruit of three botanical varieties of ciruela: fruit skin turning green to red, green to yellow or green to orange, grown throughout the year over dry and wet seasons. In vitro evaluations were carried out to observe mycelial growth, sporulation and conidial germination: Evaluations on fruit were percentage and disease severity, soluble solids content (SSC) and weight loss after 4 days storage at ambient temperature. In general, leaf extracts had better fungicidal effects than stem extracts. For in vitro studies, leaf extracts inhibited sporulation and spore germination more than mycelial development. Leaf extracts of Annona cherimola, Bromelia hemisphaerica and Carica papaya inhibited Rhizopus sporulation and rot development on the yellow variety whereas extracts of Casimiroa edulis reduced R. stolonifer rot on red ciruela. Infection spread from 25 to 100% of the fruit surface depending on extract or ciruela variety. After storage, SSC values were not significantly different. Less weight loss was observed for the orange variety than the other varieties. Further studies need to be undertaken to isolate the active compounds from those extracts with fungicidal potential. (C) 2000 Elsevier Science B.V.