Agarwood is not an aromatic material distributed uniformly throughout every tree. When trees of the genus Aquilaria experience stimuli such as injury or microorganisms, resin-containing areas form and are used as fragrant wood. Researchers are studying ways to harness this response to produce agarwood artificially.
A study published by Ding and colleagues in 2025 combined a signaling substance involved in plant defense, an acid, and a fungus to investigate conditions that promote agarwood formation. The species studied was Aquilaria sinensis. This was a two-stage study: first narrowing down candidates in detached branches, then examining chemical characteristics in growing trees.
Examining combinations of three stimuli and time
The researchers used methyl jasmonate, which is associated with plant hormone signaling; formic acid; and a culture broth of a fungal strain called A13. The fungus, Botryosphaeria rhodina, had originally been isolated from resin-containing wood of Aquilaria sinensis. Because this fungus can also cause plant disease, this is not a method intended for home replication.
First, each stimulus was applied separately to select candidate concentrations. The researchers then tested two levels each of the three concentrations and treatment duration, giving 16 combinations in total. Rather than simply changing one condition at a time, this experimental design can also examine whether the influence of one stimulus changes in the presence of another.
Detached branches were compared after 7 and 15 days of treatment. Compounds characteristic of agarwood do not necessarily accumulate sufficiently over such a short period. The researchers therefore used the total analytical signal from the components and the relative proportion of methyl jasmonate as indicators of the early response.
A short-term response is not the quality of finished agarwood
Treatment duration had the largest effect on this indicator, followed by the concentrations of methyl jasmonate and formic acid. Within the range examined, the main effect of fungal broth concentration was not statistically clear. Effects involving combinations of conditions were also observed.
The selected combination contained 1% methyl jasmonate and 1% formic acid, together with fungal broth. However, this result applies to the concentrations tested and the indicators chosen for this study. It neither proves that the fungus is unnecessary nor establishes an optimum across every possible concentration.
Methyl jasmonate was also supplied externally. Changes in the amount detected alone cannot distinguish newly synthesized material made by the tree from material applied from outside. The detached-branch indicators must be distinguished from the aroma and quality of agarwood formed over a long period.
The authors suggest that early defense-related signals may lead to subsequent production of aroma compounds. However, they did not directly demonstrate this pathway by tracing gene activity or the flow of substances.
Comparing growing trees after four and nine months
In the next stage, trees at a plantation in Zhongshan, China, were divided into three treatment groups: the selected combined inducer, the solvent 25% ethanol, and water. Liquid was introduced into holes drilled in the trunks, and wood was collected after four and nine months. Three samples were evaluated per group at each time point, for 18 samples in total.
In the tree experiment, undiluted fungal culture broth was used to simplify the procedure. The concentrations and treatment duration selected with detached branches were therefore not transferred unchanged to the long-term tree experiment.
The combined-inducer group had larger resin-containing areas than the water group, and the brown-to-black areas were thicker after nine months. Trees receiving solvent alone also showed leaf loss and damage to the wood. The aim is not simply to apply a strong stimulus, but to promote formation while maintaining the trees’ condition.
How did the researchers judge progress toward agarwood?
Beyond appearance, the researchers measured the proportion of ethanol-soluble extractives and a marker compound called agarotetrol. Agarotetrol is a chromone found in agarwood.
The comparison used the 2020 edition of the Chinese Pharmacopoeia cited in the paper. Its criteria include at least 10% ethanol-soluble extractives and at least 0.1% agarotetrol.
The three samples collected nine months after application of the combined inducer met these content criteria. Together with color reactions and other tests, the authors judged that nine months of treatment produced artificial agarwood conforming to the pharmacopoeia. The four-month samples did not meet the conditions in the same way.
Analytical patterns comprising signals from multiple components were also compared with an agarwood reference drug. The combined-inducer group showed features closer to the reference than the water-only group. Such chemical fingerprints help assess differences that a single measurement cannot adequately capture.
This does not mean the aroma matched natural agarwood
Agarwood contains various constituents, including sesquiterpenes and chromones. Combining ratios of analytical signals with measurements of chromones, the researchers discussed the possibility that the combined inducer also increased sesquiterpene accumulation. This inference was based on the ratio of signals appearing in particular retention-time ranges, not on a direct measurement of essential oil yield.
Meeting pharmacopoeial chemical criteria or showing similar analytical patterns does not mean that people would perceive the same aroma as natural agarwood. Nor did this study establish the aroma on burning, market price, or long-term safety of use.
Responses to induction also vary with individual trees and growing conditions. The long-term tree experiment was small, with three samples per condition at each time point, and did not compare every component of the combined formulation separately. Whether the same quality can be obtained consistently in other trees and locations remains an open question.
Summary
This study demonstrated an approach that first narrows down combinations of stimuli using detached branches and then examines long-term formation in growing trees. In the group receiving the selected combined inducer, samples met the chemical quality indicators of the pharmacopoeia cited in the paper after nine months.
The authors hope that approaches like this could make artificial agarwood production more efficient and help protect wild Aquilaria sinensis by supplementing demand for natural agarwood. Whether harvesting of wild trees actually decreases remains untested. Still, the research points toward understanding and cultivating tree responses rather than merely harvesting fragrant wood.
References
Ding, Q., Qin, B., Deng, S., Chen, J., Liu, Z., Zhou, W., Chen, X., Zhang, W., Zhou, X., & Gao, X. (2025). Optimization and induction effect evaluation of complex inducer of Aquilaria sinensis based on factorial design. Scientific Reports, 15, 19656. DOI: 10.1038/s41598-025-04230-x / Full original article. Original article: © The Author(s) 2025, CC BY-NC-ND 4.0.
