1. Species (Genetics)
- Different Aquilaria species produce distinct sesquiterpene and chromone profiles, which define aroma quality.
- Examples:
- A. malaccensis → Rich in α-guaiene, agarofurans, and 2-(2-phenylethyl)chromones; highly prized in Middle Eastern markets.
- A. sinensis → Slightly lighter aroma; higher proportion of eudesmanes.
- A. crassna → Stronger balsamic notes, variable chromone content.
- Genetic variation also affects resin yield and response to microbial infection.
Key point: Species choice directly determines the baseline aromatic composition.
2. Soil Type and Nutrients
- Soil pH, texture, organic matter, and nutrient content influence tree health and resin formation.
- Nutrient impacts:
- Nitrogen (N): Promotes growth but excessive N may dilute resin concentration.
- Phosphorus (P) and Potassium (K): Support resin biosynthesis and tree defense mechanisms.
- Micronutrients (Mn, Zn, Fe): Act as enzyme cofactors in terpenoid and chromone biosynthesis.
- Soil texture and drainage: Poor drainage may stress trees, sometimes enhancing resin formation as a defense response.
Key point: Soil affects resin quantity, quality, and sesquiterpene-chromone ratios.
3. Tree Age
- Resin accumulation and chemical complexity increase with tree age, but the relationship is not strictly linear.
- Observations:
- Young trees (<5 years) → Minimal resin; low sesquiterpene and chromone content.
- Mature trees (8–15 years) → Optimal balance of sesquiterpenes and chromones.
- Very old trees (>20 years) → High resin yield but some volatiles may oxidize, altering fragrance.
- Practical implication: Most commercial agarwood is harvested from trees 8–15 years old, balancing yield and aroma quality.
Key point: Age determines resin abundance, complexity, and aromatic profile.
4. Induction Method
Agarwood is formed as a defense response, so the method of induction strongly influences resin chemistry.
Types of induction:
- Natural infection / wounding
- Fungal infection (e.g., Fusarium, Lasiodiplodia spp.)
- Slow accumulation of high-quality, complex resin
- Variable yield and patchy distribution
- Artificial inoculation
- Fungal inoculation via drilling or implanting mycelium
- Produces consistent sesquiterpene and chromone levels
- Faster formation than natural infection
- Chemical induction
- Phytohormones or chemical elicitors stimulate defense pathways
- May favor certain sesquiterpene or chromone classes over others
- Mechanical wounding
- Cuts, burns, or nails
- Induces resin primarily around wound site; often lower chromone content
Key point: Induction method affects resin distribution, chemical composition, and overall aroma quality.
Summary Table: Factors vs Chemical Profile
| Factor | Influence on Sesquiterpenes | Influence on Chromones | Influence on Aromatics | Notes |
|---|---|---|---|---|
| Species | Determines types & abundance | Determines chromone variants | Minor effect | Baseline genetic signature |
| Soil & Nutrients | Affects enzyme activity & terpene synthesis | Modulates chromone accumulation | Minor effect | Stressful soils can enhance resin |
| Tree Age | Older trees → higher sesquiterpene levels | Chromones accumulate over time | Aromatics more complex | Optimal harvest: 8–15 years |
| Induction Method | Type & intensity dictate sesquiterpene patterns | Strongly affects chromone profile | Can increase volatile aromatics | Choice of method balances yield & quality |