This study was conducted to screen the endophytic bacteria as a biological control agent (BCA) against Ganoderma boninense. A total of 581 endophytic bacteria were successfully isolated from symptomless oil palm root tissues at Teluk Intan, Perak, Malaysia. Three endophytic bacteria, Pseudomonas aeruginosa GanoEB1, Burkholderia cepacia GanoEB2, and Pseudomonas syringae GanoEB3 were found to have a potential as BCA based on their percentage inhibition of radial growth (PIRG) in dual culture and culture filtrate tests. Two nursery trials were conducted to evaluate the capability of these bacteria to suppress Ganoderma disease in oil palm seedlings that were artificially infected with G. boninense using rubber wood block (RWB) sitting technique. The percentage of disease incidence (DI), severity of foliar symptoms (SFS) and dead seedlings were used as the assessment tools. As a result, DI and SFS have developed much slower in the seedlings that were pre-treated with bacteria compared to untreated seedlings. After 6 months of inoculation, Ganoderma disease incidence was reduced from 62-75% in the seedlings treated with P. aeruginosa GanoEB1, followed by B. cepacia GanoEB2 (31-59%) and P. syringae GanoEB3 (30-31%). Among these three endophytic bacteria, P. aeruginosa GanoEB1 was the most effective in controlling Ganoderma disease and the dead seedlings were in the range of 13.3-26.7%, followed by B. cepacia GanoEB2 (33.3% for both trials) and P. syringae GanoEB3 (33.3-40.0%) compared to untreated seedlings at 60% for both trials. A field study needs to be conducted to verify their effectiveness in controlling Ganoderma in oil palm.
Bud rot disease is a damaging disease of oil palm in Colombia. The pathogen responsible for this disease is a species of oomyctes, Phytophthora palmivora which is also the causal pathogen of several tropical crop diseases such as fruit rot and stem canker of cocoa, rubber, durian and jackfruit. No outbreaks of bud rot have been reported in oil palm in Malaysia or other Southeast Asian countries, despite this particular species being present in the region. Analysis of the genomic sequences of several genetic markers; the internal transcribe spacer regions (ITS) of the ribosomal RNA gene cluster, beta-tubulin gene, translation elongation factor 1 alpha gene (EF-1α), cytochrome c oxidase subunit I & II (COXI and COXII) gene cluster along with amplified fragment length polymorphism (AFLP) analyses have been carried out to investigate the genetic diversity and variation of P. palmivora isolates from around the world and from different hosts in comparison to Colombian oil palm isolates, as one of the steps in understanding why this species of oomycetes causes devastating damage to oil palm in Latin America but not in other regions. Phylogenetic analyses of these regions showed that the Colombian oil palm isolates were not separated from Malaysian isolates. AFLP analysis and a new marker PPHPAV, targeting an unclassified hypothetical protein, was found to be able to differentiate Malaysian and Colombian isolates and showed a clear clade separations. Despite this, pathogenicity studies did not show any significant differences in the level of aggressiveness of different isolates against oil palm in glasshouse tests.
Phytophthora palmivora has caused disease in many crops including oil palm in the South America region. The pathogen has had a significant economic impact on oil palm cultivation in Colombia, and therefore poses a threat to oil palm cultivation in other regions of the World, especially in Southeast Asia, the largest producer of the crop. This study aimed to look at the ability of isolates from Malaysia, Colombia, and other regions to cross-infect Malaysian oil palm, durian, and cocoa and to develop specific biomarkers and assays for identification, detection, and diagnosis of P. palmivora as a key component for the oil palm biosecurity continuum in order to contain the disease especially at the ports of entry. We have developed specific molecular biomarkers to identify and detect Phytophthora palmivora using polymerase chain reaction (PCR) and real-time loop mediated isothermal amplification (rt-LAMP) in various sample types such as soil and plants. The limit of detection (DNA template, pure culture assay) for the PCR assay is 5.94 × 10-2 ng µl-1 and for rt-LAMP is 9.28 × 10-4 ng µl-1. Diagnosis using rt-LAMP can be achieved within 30 min of incubation. In addition, PCR primer pair AV3F/AV3R developed successfully distinguished the Colombian and Malaysian P. palmivora isolates.