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' f ruit (red mombin) (Spondias purpurea L.) during handling and storage. To ev aluate the fungicidal potential of plants indigenous to the state of Morelo s, Mexico, aqueous extracts of leaves or stems of 19 different plant specie s were tested against Rhizopus development in vitro and in vivo. Extracts w ere applied to fruit of three botanical varieties of ciruela: fruit Skin tu rning green to Icd, green to yellow or green to orange, grown throughout th e year over dry and wet seasons. In vitro evaluations were carried out to o bserve mycelial growth, sporulation and conidial germination. Evaluations o n fruit were percentage and disease severity, soluble solids content (SSC) and weight loss after 4 days storage at ambient temperature. In general, le af extracts had better fungicidal effects than stem extracts. For in vitro studies, leaf extracts inhibited sporulation and spore germination more tha n mycelial development. Leaf extracts of Annona cherimola, Bromelia hemisph aerica and Curica papaya inhibited Rhizopus sporulation and rot development on the yellow variety whereas extracts of Casimiroa edulis reduced R. stol onifer rot on red ciruela. Infection spread from 25 to 100% of the fruit su rface depending on extract or ciruela variety. After storage, SSC values we re not significantly different. Less weight loss was observed for the orang e variety than the other varieties. Further studies need to be undertaken t o isolate the active compounds from those extracts with fungicidal potentia l. (C) 2000 Elsevier Science B.V. All rights reserved.