Current R&D towards better management of ganoderma control

Basal siem rol (BSR) of oil palm (OP) by Ganoderma boninense is of major economic concern and it is the predominant disease of OP in SE Asia. Inspite of enormous progress made over the past years with respect to the biology, epidemiology of the pathogen Ganoderma boninense, and management of the disease, BSR contimed to be the principal limiting factor in oil palm production. The principle control measures adopred by oil palm plantations are aimed at minimizing the incidence of the disease in a replanting prolonging the productive life of the infected palm, and deloving the progress of Ganoderma infection. In so doing, most plantations continue to avoid losses through stringent compliance of the integrated holistic management approaches. The present report however, discusses on the R&D currently being carried out towards a better understanding of the disease problem and possible reflections on enhancing Ganoderma control Early detection of symptoms is crucial for control, although effective methods remain elusive. Our research studies compared dominant detecTable Ganoderma metabolite (ergosterol) concentration in sound and decayed OP seedlings and mature plants. G. boninense biomass was correlated with ergosterol concentration in vitro and furthermore, the metabolite was correlated with internal colonisation (a) of inoculated seedlings. (b) of felled and standing OP and (c) to external symptoms of the disease. Ergosterol was not detected in healthy samples. As the BSR disease can be considered as a white rot process where fungal biomass will increase in the OP from a low to high level, treatments may be made more effective as the amounts of biomass can be estimated and early detection may be possible, enabling early remedial actions to be taken Over the years, field management of BSR has focussed onthe agronomic and cultural practices (sanitation, surgery and mounding and use of chemicals, although manipulation of N. P and K has shown some interesting observations. Considering the infection pathway of Ganoderma is by degrading the lignin component of the wood, the ideal solution to address the emergence of BSR is to reinforce the oil palm roots by manipulating lignin with plant nutrients.Applications of copper and calcium ions produced lignin-related enzymes, suach as peroxidase (POD) and laccase as well as hydrogen peroxide (H20) Lignin biosynthesis is highly influenced by the availability of H2O, POD and laccase. Both calcium and copper treated roots showed a greater lignification of cell walls and an increase in xylem parenchyma cells of the vascular cylinder, all consistent with an increase in lignin production. Scanning electron microscopy analysis of copper and calcium-treated issues revealed the cell wall between adjacent parenchyma cells to be thicker. The lignified xylem parenchyma cells could be a provisional physical barrier to slow down the penetration and spread of Ganoderma which can be employed with other methods to enhance the host resistance during infection. The role of 35 . Proceedings of the Third MPOB-IOPRI International Seminar: Integrated Oil Palm Pests and Diseases Management enzymes in cell wal degrdation during pathogenesis and the possible intervention of enzymes inhibitors can be an option to slow down spread of BSR. Biological control need not necessarily be a cure for BSR but can merely arrest the disease spread by inoculation with a biocontrol agent. Introducing microorganisms to the roots to control BSR is to manipulate indigenous communities of the roots in a manner, which leads to enhanced suppression of Ganoderma. We are looking into the possibility of developing an endophytic microbial consortium as biopretreatment of seedlings at nursery stage with the aim of increasing the host's resistance against infection in the fields. In addition amendments to planting holes can induce soil suppresiveness towards Ganoderma. Endophytic bacteria and mycorrhizal fungi (AMF) have been chosen based on their in vitro biological activity. They are compatible and the effect of the bacteria on the mycorrhizal fungi resembled that of a mycorrhiza helper bacteria (MHB) association because the association significantly promoted germination of AMF spore and increase in hyphal length. The use of these endophytic bacterial isolates to increase plant protection in combination with AMF opens up the possibility of using dual bacteria-fungal preinoculation as a promising approach for controlling BSR in oil palm and needs to be further exploited. However, these approaches are provisional methods forcontrolling Ganoderma infection in OP which can be employed with other existing methods of control. Until resistant varieties are developed and made available, the research on remedial measures for BSR has to be intensified for continual improvement of existing methods of control.