Antifungal activity of extracts of extremophile plants from the Argentine Puna to control citrus postharvest pathogens and green mold

Abstract

A main constraint on the citrus industry is the management of postharvest diseases, mostly of fungal origin. The fungicides used to control these diseases: (1) leave persistent residues that raise some dietary concerns; (2) cannot be used on fruit produced under ‘organic’ rules; and, (3) have experienced resistance to them become widespread within citrus packinghouses. Consequently, the development of management strategies to supplement or replace the use of synthetic fungicides by the utilization of microorganisms or natural bioactive products is desirable. The aim of this work was to screen extremophile plants from the Argentine Puna in order to select species with antifungal activity against Penicillium digitatum and Geotrichum citri-aurantii, two very important fungal species causing citrus postharvest disease. Plant aqueous extracts obtained from Chuquiraga atacamensis, Parastrephia phyliciformis and Parastrephia lepidophylla, were able to inhibit in vitro P. digitatum growth, while P. lepidophylla extract was active against G. citri-aurantii cultures. P. lepidophylla aqueous formulations showed MIC100 values of 300 mg/L against both P. digitatum and G. citri-aurantii strains. MFC values of P. lepidophylla extracts were similar to MIC100 values. In vivo tests showed that the P. lepidophylla aqueous formulations (600 mg/L) exert curative and protective effects on the fruit against infection by a P. digitatum wild strain.