Antimicrobial and nematicidal screening of anamorphic fungi isolated from plant debris of tropical areas in Mexico

Abstract

Forty seven fungal strains were isolated from plant debris in the tropical regions of Mexico, where fifteen of them were identified to species and twenty two to genus level. All isolates were grown in fermented rice and their EtOAc extracts screened against ten targets, four bacteria (Bacillus subtilis,Erwinia carotovora, Staphylococcus aureus and Xanthomonas campestris), the yeast Candida albicans, three phytopathogenic fungi (Alternaria tagetica, Colletotrichum gloeosporioides andFusarium oxysporum), the Oomycete Pythium aphanidermatum and the nematode Meloidogyne incognita. Antimicrobial activity was detected in 18 isolates against at least one of the target strains tested. Seven of these isolates with broad spectrum activity, which were defatted and their minimum inhibitory concentrations (MICs) were determined by microdilution assay. The greatest antagonistic action was produced by Cylindrium elongatum with broad spectrum activity while Corynespora cassiicola and Memnoniella sp. MR33 showed moderate antimicrobial properties. On other hand, in vitro nematotoxic activity was clearly detected only in Selenosporella sp. GH26 with 91 (LD50) and 147 µg/ml (LD90). This is the first report on the isolation and biological evaluation of anamorphic fungi from some Mexican tropical regions, demonstrating their potential as a source of biologically active natural metabolites for use in future applications in agriculture or pharmacy. Key words: Anamorphic fungi, antimicrobial, Corynespora, Cylindrium, fungal extracts, nematicide,Selenosporella, Yucatan peninsula.