Tissue culture (micropropagation & organogenesis) overview

1. What is Tissue Culture?

• Tissue culture is a biotechnological propagation method where small plant tissues (explants) are grown under sterile conditions on a nutrient medium.
• Allows rapid multiplication of elite Aquilaria plants with desirable traits such as:
  • High resin content
  • Disease resistance
  • Fast growth

2. Micropropagation

• Definition: Rapid multiplication of plants from small explants (shoots, buds, or meristems).
• Steps:
  1. Explant Selection: Apical shoots, nodal segments, or young leaves.
  2. Sterilization: Surface sterilization using NaOCl or H₂O₂ to prevent microbial contamination.
  3. Culture Initiation: Place explant on nutrient medium containing macro/micronutrients, vitamins, carbon source (sucrose), and growth regulators.
  4. Shoot Multiplication: Use cytokinins (e.g., BAP) to stimulate multiple shoots.
  5. Rooting Stage: Transfer shoots to root-inducing medium with auxins (e.g., IBA, NAA).
  6. Acclimatization: Gradually expose plantlets to external conditions (shade house → nursery → field).

Advantages:

• Produces hundreds to thousands of uniform plants in a small area.
• Disease-free and genetically uniform plants.
• Faster than seed propagation.

Limitations:

• Requires sterile lab facilities and skilled technicians.
• Higher cost per plant initially.
• Some species may exhibit somaclonal variation (genetic differences).

3. Organogenesis

• Definition: Formation of new organs (shoots, roots) from callus tissue or explants in vitro.
• Types:
  • Direct Organogenesis: Explants form shoots or roots directly without an intermediate callus.
  • Indirect Organogenesis: Explants first form callus, which then differentiates into shoots/roots.

Steps:

1. Explant excision and sterilization.
2. Placement on callus induction medium with auxin-cytokinin combination.
3. Callus differentiation into shoots and roots.
4. Transfer to rooting medium and later acclimatization.

Advantages:

• Enables propagation of elite, high-resin genotypes.
• Can rescue endangered species or rare genotypes.
• Facilitates genetic improvement or secondary metabolite production in vitro.

Limitations:

• Labor and resource-intensive.
• Requires careful monitoring to avoid contamination and ensure proper differentiation.

4. Applications in Agarwood Cultivation

• Rapid multiplication: Produce large numbers of trees from limited high-quality parent plants.
• Conservation: Propagate endangered native Aquilaria species in controlled conditions.
• Genetic improvement: Select for high oil/resin yield, disease resistance, and stress tolerance.
• Research & Resin Production: Callus cultures can be used for in vitro resin induction studies.

5. Key Takeaways

• Tissue culture (micropropagation + organogenesis) is a high-tech, high-yield propagation method for Aquilaria.
• Produces uniform, disease-free plants faster than seed or cutting propagation.
• Supports commercial plantations, conservation, and research applications.
• Requires lab infrastructure, skilled staff, and careful acclimatization for successful field establishment.

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