In vitro assessment of antifungal activities of antagonistic fungi towards pathogenic Ganoderma boninense under metal stress

•Metal species and concentrations influenced growth of antagonistic fungi.•Fungal growth under metal stress is closely correlated to antifungal activities.•Trichoderma sp. has good tolerance and antifungal activities under metal stress.•Cd2+, Zn2+ and Cu2+ has higher toxicity to fungi than Al3+ and Pb2+.

Three antagonistic fungi (Trichoderma asperellum isolate T2, Diaporthe sp. isolate WAA02, Penicillium citrinum isolate BTF08) were evaluated for their tolerance to metals and the impact of the metals on their antifungal expression against a model pathogen (Ganoderma boninense). Experiments performed include metal tolerance and dual culture assays, viability test, SEM and Pearson Correlation test. In the presence of metals, growth and antifungal expression of the endophytes were inhibited, particularly by Cd2+ (50 ppm), Zn2+ (100 ppm), and Cu2+ (100 ppm). The antifungal expression was least affected by the presence of Pb2+ (60–100% inhibition) but was 0% in Al3+, Cd2+, Cu2+ and Zn2+ (200 ppm onwards). The absence of antifungal expression was associated with their poor growth in these metals (r = 0.6080–0.8911). Clearly, the growth and antifungal activity of these isolates are influenced by the metal species and concentrations, and is an important factor for future development of antagonistic fungi as biopesticides.

Graphical abstractMetal stress influenced the growth and antifungal activities of antagonistic fungi.Figure optionsDownload full-size imageDownload as PowerPoint slide