A new screening method for <i>Ganoderma philippii</i> tolerance in tropical Acacia species §

Abstract

Red root rot disease caused by Ganoderma philippii is one of the most economically important diseases of tropical Acacia species. Research on field control of the disease has to date focused on inoculum reduction, silviculture practices and application of biological control agents. Incorporation of tolerant genotypes, a key component of integrated disease management, has not been adequately explored because of a lack of reliable and quick screening protocols. Recently, we developed a more rapid method of screening for red root rot tolerance in Acacia mangium, A. crassicarpa and A. mangium x A. auriculiformis hybrid planting stock, in which groups of five, 6-week-old plants were subjected to inoculum consisting of a rubber (Hevea brasiliensis) wood block culture of the pathogen held within a polythene bag. As symptoms start to appear 10 weeks after inoculation, experiments can be  completed in a six-month period instead of the years needed by the traditional pot system. Using this technique we were able to identify variations in tolerance and/or susceptibility to G. philippii in A. mangium, A. crassicarpa and A. mangium x A. auriculiformis hybrid planting stock in a more consistent manner. Tolerant and susceptible genotypes subsequently have been selected for further experiments or crosses. While the ultimate goal of this study was to develop and deploy  high-yielding Acacia genotypes that are also tolerant to red root rot disease, results of the current screening studies may also be used to investigate the basis for tolerance to G. philippii in Acacia species.

Keywords: Acacia mangium, disease management, plantation forestry, red root rot