Antagonistic Effects of Endophytic Bacteria against Ganoderma Boninense Observed through Microscopy and Examination of Bacterial Β-1,3-Glucanase Expression

Yew, Kai Yi (2023) Antagonistic Effects of Endophytic Bacteria against Ganoderma Boninense Observed through Microscopy and Examination of Bacterial Β-1,3-Glucanase Expression. Final Year Project (Bachelor), Tunku Abdul Rahman University of Management and Technology.

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Abstract

The fungus plant pathogen Ganoderma boninense is recognised and remained as a major obstacle in causing Basal Stem Rot (BSR) disease within the oil palm industry, particularly in South-East Asia. Early studies of biological control of wood-decaying fungi have drawn attention to endophytic bacteria due to their potential antagonistic effect in controlling pathogenic fungi. However, the specific mechanisms of endophytes attacking action are not clear and there are not many studies focusing on the interaction between endophytic bacteria with Ganoderma boninense. In this study, a dual culture assay was first conducted to confirm the inhibition of previously identified endophytic bacteria against PER71’s growth in vitro. It was found that SL14(1), SL14(2), and SL22(YC) has an average percentage inhibition of radial growth (PIRG) with more than 80%. To demonstrate the antagonistic behaviour of Ganoderma boninense (PER71) with SL14(1), SL14(2), and SL22(YC) respectively, their interactions were examined microscopically. The results showed that bacteria induced holes or openings in the fungal cell wall and caused fragmentation of the fungal hyphae. Besides, the activity of cell wall-degrading enzymes (CWDEs): β-1,3-glucanases as a defensive mechanism of mode of actions from endophytic bacteria was examined using β-1,3-glucanase assay. It was demonstrated that these three bacteria strains exhibited activities of β-1,3-glucanases expression, with SL14(2) having the highest amounts of β-1,3-glucanases followed by SL22(YC) and SL14(1). Based on microscopy examination and β-1,3-glucanase assay, we suggest that necrotic hyperparasitism may be the mode of action undertaken by these three endophytic bacteria strains to inhibit Ganoderma boninense. Keywords: Ganoderma boninense, endophytic bacteria, cell wall-degrading enzyme, β-1,3-glucanase.