In natural conditions, the agar or Oud is formed due to fungus-host interaction, which usually occurs after boring by the larvae of a stem borer, Neurozerra conferta Walker (= Zeuzera conferta Walker). The natural infection by certain fungi and bacteria starts in the wood of A. malaccensis after the boring by the stem borer. Naturally, agarwood formation is often linked to the physical wounding or damage of the trees caused by thunder strikes, animal grazing, pest and disease infestations (Rasool & Mohamed, 2016; Wu & al., 2017). These events expose the inner part of the trees toward pathogenic microbes, which elicit the defence mechanism of Aquilaria to initiate resin production (Tan & al., 2019). In Dibrugarh district, agar chips formed specifically by infection arising from woodpecker’s strike are locally known as ‘Soraikhuli’ (‘Sorai’ = bird, ‘-khuli’ = opening).
This occurs when the woodpecker strikes and creates an opening in the agar trees, looking for the borer worm or for laying eggs. This often leads to a significant amount of infection building up there. Usually, plants above the age of seven years are vulnerable to infection by the fungus. However, the initiation of natural infection is observed in several plants with an age of less than two years in certain parts of Assam, Manipur, and Tripura. The natural infection is usually established after a few to several years of initiation of infection for producing a significant quantity of agarwood. The resin is secreted by the trees as a defence reaction and deposited around the wounds over the years following the injury, where the accumulation of the volatile compounds eventually forms agarwood (Subasinghe & Hettiarachchi, 2013). The Rain Forest Research Institute, Jorhat,
identified three fungi responsible for agarwood formation (Borah, 2015). The fungus Phialophora parasitica Ajello, Georg & C.J.K. Wang is reported to be responsible for the formation of agarwood in the plantations of West Bengal. A few fungal isolates, like Fusarium sp., Rhizophora sp., Aspergillus sp., and Mucor sp. were also isolated from the infected host tissue. Four endophytic fungi (Alternaria sp., Curvularia sp., Rhizopus sp. and Sterilia sp.) are isolated from juvenile (1-year-old) A. malaccensis plant and three fungal colonies (Penicillium sp., Fusarium sp., and one putative Cladosporium sp.) were isolated from agarwood chips by Mochahari & al. (2020) from the samples collected in Assam. The naturally infected agar-forming trees can be identified by the presence of borer holes, oozing of liquids from the new borer holes,
closed borer holes having some typical marks, accumulation of frass at the base of the tree, presence of longitudinal cracks, presence of ants in the cracks and borer holes etc. Often the infected trees have stunted growth, poor crown, and hollow sounds on sticking or hammering.
The ‘Z Black Diamond Agarwood LLP’ under guidance MR Tamjid Ali , MD of Z Black Diamond Agarwood LLP & also Head Coach of our company
Uhud Oud has
developed 3 types of techniques for artificial induction of agar formation. According to them, these
techniques have been recognised and proven to be the best inoculation techniques to date and have
a 100% success rate. The techniques are:
1. DTII (Direct Trunk Injection of Inoculum),
2. TIIC (Trunk Injection of Inoculum through Cannula)
3. PIBR (Pasting of Inoculum through Bark Removal)
In DTII, their inoculation experts do the injury through drill machines with proper precision. After this process, the inoculum is injected in the tree trunk through the drill holes. This process is repeated in another 60 days and left for a few months. In TIIC method, the inoculum is injected through a cannula for a more extended period after the drill injury. This process requires a larger amount of inoculum, but the quantity of agar obtained is quite high; thus, this is the most popular artificial inoculation method. In PIBR method, the tree is injured through deep cuts in the tree trunk, a little deeper than the bark of the tree, and the inoculum is pasted in the injured areas. They offer their service mostly on a percentage basis (usually 70% company: 30% grower but varies from case to case). The company also claims that they only uses herbal formulations for artificial induction.
