Fungitoxicity of Trichoderma longibrachiatum (Rifai) metabolites against Fusarium oxysporum, Aspergillus niger and Aspergillus tamarii

Abstract

An experiment was carried out to evaluate the fungitoxic effect of Trichoderma longibrachiatum (Rifai) metabolite on Fusarium oxysporum, Aspergillus niger and Aspergillus tamarii. The fungi were collected from the International Institute of Tropical Agriculture (IITA) and the Nigerian Institute of Science Laboratory Technology (NISLT). Trichoderma longibrachiatum was cultured on one-quarter strength Potato Dextrose Broth (PDB) following standard procedures. Its metabolite was extracted using 50 ml n-hexane with 50 ml Potato Dextrose Broth (PDB). The metabolite was purified by filter sterilization using a sterile 0.22 µm millipore filter disc after centrifugation at 900 rpm for 20 minutes.

Petri plates of each fungus were impregnated in triplicates with the T. longibrachiatum metabolites using four concentrations (10%, 25%, 50% and 100%) and three volumes (1 ml, 2 ml and 3 ml). Petri plates of fungi without the metabolite and Petri plates of fungi treated with n-hexane and PDB served as controls. All Petri plates were incubated at 28°C for seven days. Radial and diametric growth of each fungus on all Petri plates were measured daily at 24-hour intervals. Data obtained were analysed using SAS (version 9.3).

Growth inhibition of Fusarium oxysporum, Aspergillus niger and Aspergillus tamarii was significantly higher than in the control, in that order (P ≤ 0.05). Inhibition of the fungi by metabolites extracted with both PDB and n-hexane was significantly better than in the control. Generally, inhibition by metabolite extracted with PDB was better than that extracted with n-hexane. Growth inhibition at all concentrations of the metabolite was significantly greater than in the control (P ≤ 0.05). Generally, inhibition at 100%, 50% and 25% concentrations was better than that at 10% concentration of the metabolite.

Trichoderma longibrachiatum metabolite can therefore be said to possess promising fungitoxic potential even at concentrations as low as 25%. Both PDB and n-hexane are effective extraction media for the metabolite.