Abstract

This study evaluated the antagonistic potential of Trichoderma harzianum Rifai culture and its cellulolytic β-glucosidase against four phytopathogenic fungi of oil palm: Fomitopsis. meliae, Bipolaris sorokiniana, Phoma herbarum, and Ganoderma. boninense. Antifungal activity was assessed through dual culture test, hyperparasitism interactions, and enzymatic degradation of pathogen cell-walls by enzymes produced via solid state fermentation. In dual culture test, T. harzianum Rifai inhibited mycelial growth by 92.80%, 88.70%, 80.20 %, and 98.90% against F. meliae, B. sorokiniana, P. herbarum, and G. boninense respectively, compared to control 99.90% growth in the control. Microscopic analysis of hyperparasitism revealed cell lysis of the target fungi following direct interactions with T. harzianum mycelia, indicating enzymatic digestion of fungal cell walls. Among the cell wall-degrading enzymes secreted, β-glucosidase exhibited the highest activity, with peak value of 199.3U/g, 197.6U/g, 197.8U/g, and 209.5U/g for the respective pathogens. The enzyme significantly suppressed fungal growth on agar plates. The Minimum Inhibitory Concentration (MICs) of T. cellulolytic β-glucosidase 128, 512, 32, and 64mg/mL, while the Minimum Fungicidal Concentrations (MFCs) were 32, 128, 512, and 64mg/mL, respectively. In vivo assays demonstrated that oil palm seeds treated with T. harzianum Rifai cellulolytic β-glucosidase provided superior protection to seedlings compared to soil incorporation methods. Collectively, these findings demonstrate that T. harzianum Rifai-derived cellulolytic β-glucosidase possesses strong antifungal activity and represent a promising biocontrol agent for managing fungal diseases in oil palm..

Keywords:Biocontrol; β-glucosidase; Phytopathogens; Trichoderma harzianum rifai; Cellulolytic; Oil palm; Minimum inhibitory concentration; Minimum fungicidal concentration