Inducing agarwood resin in Aquilaria trees using fungal inoculants is a key biotechnological intervention. Controlled, on-site inoculation maximizes resin yield and quality while ensuring tree health, environmental safety, and regulatory compliance.
1. Selection of Trees for Inoculation
Criteria:
- Age: Typically 3–8 years old, depending on species and tree size.
- Health: Trees must be disease-free and vigorous.
- Genotype: Preferably high-resin producing clones identified via chemical markers or previous studies.
Documentation:
- Record tree ID, age, location, and previous treatments.
- Mark inoculation points for traceability.
2. Selection of Microbial Inoculants
Common Fungal Agents:
- Fusarium oxysporum – induces resin through stress response.
- Lasiodiplodia theobromae – effective in promoting heartwood resin.
- Dual-action formulations (e.g., MnO₂ + Fusarium oxysporum) improve induction efficiency.
Quality Control:
- Use verified, non-pathogenic strains.
- Maintain pure cultures under controlled lab conditions.
- Test inoculants for viability, purity, and compatibility before field application.
3. Preparation of Inoculum
- Grow fungi on solid or liquid media to produce spores or mycelial suspension.
- Adjust concentration: typically 10⁶–10⁸ CFU/mL (colony-forming units per mL).
- Add co-inducers (e.g., MnO₂ + sugar) if using dual-action formulations.
- Keep inoculum fresh, sterile, and properly labeled until use.
4. Wound Creation and Inoculation Methods
Techniques:
- Drilling Method
- Drill holes (~1–2 cm diameter, 10–20 cm depth) at chest height.
- Insert fungal inoculum or agar plug.
- Seal with sterile biodegradable plugs or wax.
- Fracture / Trunk Injection
- Create small cuts or splits in heartwood.
- Apply liquid inoculum directly into the wound.
- Syringe / Needle Injection
- Inject spore suspension into pre-drilled holes.
- Allows precise dosing and minimal tree damage.
Best Practices:
- Limit number and size of wounds per tree to avoid stress.
- Rotate inoculation points in multi-year cycles.
- Record inoculation date, method, and inoculum used.
5. Post-Inoculation Care
- Monitor tree health and avoid additional stress (drought, pests, pruning).
- Maintain soil fertility and irrigation to support tree recovery.
- Inspect wounds periodically for resin formation, infection, or contamination.
6. Resin Monitoring and Harvesting
- Resin typically develops 6–12 months post-inoculation depending on species and environmental conditions.
- Assess resin quantity, color, density, and aroma.
- Harvest selectively, ensuring tree longevity.
- Maintain samples for chemical profiling (GC-MS/HPLC) to evaluate quality.
7. Biosafety and Environmental Considerations
- Follow BSL-1 or BSL-2 containment for inoculum preparation and handling.
- Wear PPE: gloves, masks, protective clothing.
- Prevent runoff of inoculants into soil or waterways.
- Dispose of used tools and excess inoculum safely.
8. Documentation and Traceability
- Record:
- Tree ID and location
- Inoculum strain and concentration
- Method of inoculation
- Wound location and size
- Date of inoculation and subsequent resin assessments
- Optional: Use digital or blockchain-based traceability to track resin quality and origin.
9. Advantages of Controlled On-Site Microbial Inoculation
| Benefit | Description |
|---|---|
| High resin yield | Fungal agents trigger strong secondary metabolite production |
| Superior quality | Controlled inoculants increase sesquiterpene and chromone content |
| Sustainable | Minimizes wild harvesting and tree loss |
| Traceable | Proper documentation supports CITES compliance and export requirements |
| Efficient | Reduces time to harvest vs natural infection |
Summary
Controlled microbial inoculation on-site enables efficient, sustainable, and traceable agarwood production, balancing economic benefits, tree health, and environmental safety. Proper strain selection, inoculation technique, and monitoring are key to maximizing resin yield and quality.