In Vitro Assessment of Endophytic Bacterial Isolates as Biological Control Agents Against Ganoderma Boninense

Allfeat, Mary Anne (2026) In Vitro Assessment of Endophytic Bacterial Isolates as Biological Control Agents Against Ganoderma Boninense. Final Year Project (Bachelor), Tunku Abdul Rahman University of Management and Technology.

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Abstract

Basal Stem Rot (BSR), caused by the fungal pathogen Ganoderma boninense (G.boninense), remains a critical threat to the oil palm industry, necessitating sustainable alternatives to conventional chemical fungicides. This study investigates the potential of four endophytic bacterial strains—SL14(1), SL14(2), LLT, and YC—as biological control agents. The antagonistic efficacy of these isolates was evaluated using dual culture assays. The findings demonstrate that the optimal nutrient broth to potato dextrose agar, NB:PDA ratio varied among the bacterial isolates. A 2:1 NB:PDA ratio resulted in higher percentage inhibition of radial growth (PIRG) values for SL14(2) and LLT, indicating stronger antagonistic activity against G. boninense under this condition. Conversely, SL14(1) and YC showed higher PIRG values in the 2:2 NB:PDA medium, suggesting that a more balanced medium composition was more conducive to their inhibitory effects. Furthermore, culture filtrate assays were conducted to assess the inhibitory power of bacterial secondary metabolites and revealed that all bacterial treatments significantly reduced fungal growth compared to the control. Microscopic examination of G.boninense hyphae following exposure to the bacterial isolates showed distinct morphological abnormalities which included fragmentation and shrunken hyphal structures. Taken together, our results confirm that these endophytic isolates successfully inhibit G. boninense growth in vitro, suggesting their potential as effective biocontrol agents. Further investigation is required to characterize the specific biochemical mechanisms of inhibition and evaluate their performance under field conditions.