Understanding Agarwood Formation and Its Challenges

Abstract

The resinous portion of the Aquilaria tree is called agarwood, a valuable non-timber product being used as medicine and incenses in Asia, Middle East, and Europe. Driven by high demand, the wild resources of agarwood-producing trees have been greatly threatened. This fragrant product contains many aromatic substances and is obtained from the pathological conditions of the wood of living trees. The knowledge regarding the technology for inducing agarwood and its continuous formation in the tree is still limited. To conserve the wild Aquilaria spp. and to supply sustainable amount of agarwood, cultivation of Aquilaria trees in combination with induction through artifi cial technique is seen as the best approach. In this chapter we will discuss the fundamentals of agarwood formation in the producing trees, the molecular pathway in its synthesis, current methods applied for agarwood induction in cultivated trees, and fi nally the factors infl uencing agarwood yield and quality.

History of Use and Trade of Agarwood

“…were classified as being critically endangered with Ban extremely high risk of extinction in the wild in the immediate future.Î n recognition of the dwindling state of agarwood resources (Newton and Soehartono 2001) (CITES 2017). The high prices paid for agarwood products have stimulated activity in the cultivation of the tree (Hoang Ha and Nghi 2011) and renewed interest in artificial stimulation of agarwood formation (Liu et al 2013;Rasool and Mohamed 2016;Zhang et al 2012). These initiatives are considered to potentially create alternative sources of agarwood and increase the availability of agarwood product in the marketplace (Nakashima et al 2005;Persoon 2008).…”

“…The resin, is widely used for the production of incense and perfume (essential oils) and for medical purposes (Mohamed and Lee 2016;Rhind 2014). The valuable resin develops and accumulates in the stem and branches of the tree after a process of injury and fungal infection (Bose 1938;Donovan and Puri 2004;Rasool and Mohamed 2016;Sangareswari et al 2016), but this process occurs in only a few trees in wild populations (Ng et al 1997;Paoli et al 2001). The demand for and trade in agarwood continues today, and with increasing wealth in consumer countries over recent decades, demand exceeds supply (Barden et al 2000;Chakrabarty et al 1994;Compton and Ishihara 2006).…”

Time-based LC-MS/MS analysis provides insights into early responses to mechanical wounding, a major trigger to agarwood formation in Aquilaria malaccensis Lam

“…25 Mechanical wounding could induce early response in WR genes during the rst 3 h. 26 In fact, mechanical wounding has been acknowledged as being the primary cause for the formation of agarwood. 27 Damage by mechanical wounding causes the A. malaccensis tree to weaken and become vulnerable to threats by biotic and abiotic agents. Known to be a component in the Aquilaria plant defense system, agarwood acts to close the wound and protect the tree from further pathogen or fungal invasion.…”

“…34 Although there is no specic study on brassinosteroid stimulus in Aquilaria, however, its interaction with other phytohormones such as jasmonic acid has been associated with agarwood formation. 27,30 Based on the KEGG pathway analysis, a protein with potential role in linolenic acid metabolism has been identi-ed. Linolenic acid is the precursor for lipoxygenase (LOX), which initiates the lipoxygenase and octadecanoate pathways responsible for the formation of jasmonic acid.…”

Damaging Insect Pests and Diseases and Their Threats to Agarwood Tree Plantations

“…In fact, in nature, agarwood formation relies very much on the interaction between the trees and the associated insects and microbes. The induction of agarwood formation in tree stems is often related to fungal infection, which triggers the tree's defense system to produce agarwood resin (Rasool & Mohamed 2016). So far, a wide variety of fungal species have been associated with agarwood formation (Mohamed et al 2010;Premalatha & Kalra 2013), most of which are endophytic fungi that coexist naturally with the trees and do not pose any major threats (Turjaman et al 2016).…”