The Cropwatch Files

The agarwood Files

                                     

 

Agarwood Microbiology

 

 

Copyright Tony Burfield 2005

 

 

 

Various fungi are associated with gaharu formation although it is still not absolutely clear which are important or even necessary. Infection and gaharu formation appears to be a slow process and Hooper (1904) had noted that trees that were at least 50 years old yielded the largest amounts of oleoresin. Bose (1934) isolated a member of the fungi imperfecti from the diseased wood of A. agallocha: Sadgopal (1959) comments that a Torula sp. isolated by Bose inoculated into A. agollocha trees successfully produced agar formation, but the experiments were abandoned in 1931 because of contamination of the inoculum stock. Further work by Bose involved the successful use of a Cladosporium sp. but the trees were subsequently destroyed. A later repeat of the work yielded no postive results.

 

Following this, Battcaharrya (1952) isolated Epicoccum granulatum from infected wood, and together with Sadopal (1960) and Varma (1977) further investigated the possibility that agaru formation was due to fungal activity, and the prospect of deliberately infecting trees with the causative agents became a popular goal, but the literature often showed conflicting results. One serious contender for the infectious agent was the pathogenic fungus

 

Philophora parasitica, identified by Gibson (1977) and earlier by  Hawksworth et al. (1976), who ascribed spiral cavitation of the tracheid walls of the wood of A. agallocha to this organism. Gibson indicated that the most frequently isolated fungi from infected wood also include Pencillium citrinum, Aspergillus tamarii, and other Aspergillus spp., Fusarium solani, Botryodiplodia theobromae and others. But there were several reports that Phialophora parasitica was frequently associated with better quality portions of agaru. It emerged however (Gibson 1977; Rahman 1980) that gaharu formation rarely occurred in trees under 25 years old, and formation probably followed injury to the tree, for example following wind or storm damage. Yu Chenhung  (1980) working independently in the S. China Institute of Botany in Guangzhou with A. sinensis, note that no scented oleoresin or secretory tissues were found, but when traditional drug-gatherers cut notches in the trunk, oleoresin was formed after mycelia had been observed leading to infection of the cells containing starch cells.

 

Jaluddin (1977) isolated the fungus Cytosphaera mangiferae Died. from the diseased wood  of standing trees, indicating this to be the causative infective agent for standing trees. Tamuli et al. (1999) were able to identify four fungal species associated with A. agallocha seeds (Aspergillus sp., Fusarium sp., Penicillium sp. & Epicoccum sp.) the authors subsequently turning their attention to the A. agallocha rhizosphere (Tamuli et al. 2000a). More recently Tamuli et al. (2000) identified two fungal cultures from the diseased wood: Fusarium oxysporum Schlect. and Chaetum globosum Kunze, and succeeded in inoculating healthy wooden blocks so that colony growth occurred. In the same paper, Tamuli et al. report that they deposited these cultures with the MTCC, Institute of Microbial Technology (CSIR), Chandigarh.

 

Reports were made in 1991 (Indian Perfumer 35(1), 10) that the skill of artificial infecting of agarwood had been solved in N.E. India (in Galaghat, Jorhat and Jtojoi in Assam) making the tree wood suitable for distillation in 5-6 years. Mahindru further notes that only copper stills produce an agarwood oil quality acceptable to the trade. The Tropical Rainforest Project (see elsewhere in this document) have embarked on a program of artificial infection of agarwood trees grown in plantations. No environmental or social impact studies have been seen by Cropwatch regarding these developments, and there are fears the demand for agarwood commodities could actually increase (see Cropwatch 7).

 

A recent article by Tabata et al. (2003) describes the artificial induction of five seven year old Gyrinops versteegii trees in Matram on Lombok Island and twelve Aquilaria spp. in Pekanbaru, Sumatra by drilling eight 10cm deep by 1cm wide holes and inoculating with five Fusarium spp. including Fusarium trifosfrium. Agarwood formation was observed around the drilled sites in inoculated trees but also in control trees.

 

 

 


Please see Agarwood Bibliography at the end of Agarwood files Database database for references.