A non-invasive tissue culture system for performing artificial pathogenicity assays of Ganoderma boninense

The aim of this study was to develop a non-invasive tissue culture system that could be used to perform pathogenicity assays of Ganoderma boninense using oil palm plantlets. G. boninense is a white-rot fungus that causes basal stem rot (BSR) disease in oil palm. Three different preparations of G. boninense inoculum were used for the infectivity test: mycelial agar discs, a rubberwood sawdust substrate colonized by mycelia and an oil palm sawdust substrate colonized by mycelia. The inoculum was carefully placed on the basal area of each plantlet without wounding or inflicting any pressure on the plantlet to allow the plantlet to become naturally infected. Inoculation using either the oil palm or rubberwood sawdust inoculum achieved 100% infection of the plantlets, whereas less than 60% infection was obtained using the mycelial agar disc inoculum. Fifteen days post inoculation, plantlets infected with sawdust inoculum displayed physiological symptoms of disease that resembled to those of a typical BSR infection, including leaf wilting, necrosis and rotting bole tissue. This is the first description of the successful use of a non-invasive tissue culture technique for establishing Ganoderma infections in plantlets using a sawdust substrate as a source of inoculum.