Control of Ganoderma boninense: A Causal Agent of Basal Stem Rot Disease in Oil Palm with Endophyte Bacteria In Vitro

The objective of this study was to screen the potential endophytic bacteria to be used as a biological control for Ganoderma boninense, the major causal pathogen of Basal Stem Rot (BSR) disease in oil palm. Twenty endophytic bacteria were isolated from symptomless oil palm roots but only seven isolates showed inhibitory effect by suppressing the mycelial growth of G. boninense. The isolated bacteria were screened in vitro by dual culture assay and culture filtrate test for their antagonistic properties towards G. boninense. Four bacterial endophytes (EB2, EB4, EB5 & EB6) were established to have potential as biocontrol agents based on their percentage inhibition of radial growth (PIRG) more than 50%. There was significantly difference in inhibitory effect (p<0.05) for dual culture test and these endophytic bacteria inhibited the fungal growth by an average of 52.78, 83.33, 67.59 and 93.52%, respectively on NA medium. Culture filtrate test likewise was showed a significant different for percentage of mycelia growth (p<0.05). Endophytic bacteria EB2, EB4, EB5 and EB6 suppressed the fungal growth by an average of 56.65, 91.45, 69.48 and 97.95%, respectively. Interestingly, out of four potential endophytic bacterial isolates, two, isolates namely EB4 and EB6, produced significantly (p<0.05) higher inhibitory effect than two more isolates of EB2 and EB5. Changes of hyphae occurred in presence of both bacteria of EB4 and EB6. Deformity and shrinkage of hyphae in EB6 was more apparent than in EB4 through mycelial growth test. Identification of species for these two bacteria was done using Biolog® System where EB6 was successfully identified as Pseudomonas aeruginosa but EB4 could not be unidentified. Therefore, in vitro activities of EB4 and P. aeruginosa against G. boninense in these studies suggested that these endophytic bacteria can be used as an effective biological control agent. © 2010 Friends Science Publishers