How to Swab Agar Plates for Mushroom Cultivation: Step-by-Step Guide

How to Swab Agar Plates for Mushroom Cultivation: Step-by-Step Guide

Creating agar plates from swabs is a fundamental technique in mycology for isolating mushroom cultures, expanding genetics, or preserving unique strains. Swab plates allow you to transfer mycelium from a fruiting body, substrate, or spore print onto a sterile agar medium. This guide walks you through the process step by step.

Why Use Swab Agar Plates?

Swabbing agar plates is useful for:

  • Isolating clean mycelium from a substrate or mushroom
  • Preserving rare or exotic mushroom strains
  • Testing for contamination before expanding a culture
  • Expanding your mushroom culture library efficiently

Materials You’ll Need

  • Sterile agar plates (60mm or 100mm)
  • Sterile swabs (cotton-tipped or synthetic)
  • Alcohol or disinfectant
  • Gloves and a face mask
  • Mushroom tissue, spore print, or surface to swab
  • Flame or alcohol lamp (optional, for sterilization)
  • Clean workspace or still air box (SAB)

Step 1: Prepare Your Workspace

  1. Choose a clean, draft-free area to reduce contamination.
  3. Disinfect your workspace, hands, and gloves with alcohol or sanitizer.
  5. If using a still air box (SAB), set it up to provide a sterile environment for handling plates and swabs.

Tip: Working quickly but carefully reduces the chance of airborne contaminants settling on your plate.

Step 2: Prepare Your Swab

  1. Take a sterile swab from its packaging.
  3. Moisten the swab slightly with sterile water or leave it dry if your tissue is moist.
  5. Avoid touching the swab tip to anything non-sterile.

Step 3: Collect the Sample

From Mushroom Tissue:

  • Gently lift a small piece of tissue from the inner stem or cap, avoiding surfaces exposed to contaminants.
  • Lightly rub the swab over the tissue to pick up mycelium.

From Spore Print:

  • Lightly touch the swab to the spore-bearing surface.
  • Transfer only a small amount to avoid overloading the plate.

From Substrate:

  • Swab a small exposed piece of mycelium from the substrate, avoiding discolored or contaminated areas.

Step 4: Inoculate the Agar Plate

  1. Lift the lid of the sterile agar plate just enough to access the surface.
  3. Gently swab the agar surface in a zig-zag or streak pattern to spread the mycelium.
  5. Avoid pressing too hard to prevent gouging the agar.
  7. Close the lid immediately after swabbing.

Tip: Work quickly to reduce exposure to airborne contaminants.

Step 5: Incubation

  1. Label the plate with the species, date, and sample source.
  3. Place the plate upside-down in a clean, warm area (typical incubation range is 70–75°F / 21–24°C).
  5. Avoid direct sunlight or drastic temperature fluctuations.
  7. Check the plate daily for white, healthy mycelium growth and contamination (green, black, or fuzzy growth).

Step 6: Transferring Healthy Mycelium

  • Once clean mycelium begins to grow, you can transfer it to:
    • New agar plates for expansion
    • Grain jars or bags for larger cultivation
    • Liquid culture syringes for further propagation

Tip: Always use sterile tools when transferring to avoid contamination.

Troubleshooting Common Issues

  • Contamination: Usually appears as green, black, or pink mold. Discard contaminated plates immediately.
  • Slow growth: Ensure proper temperature, moisture, and agar quality.
  • No growth: Sample may not have viable mycelium; try a different tissue or spore source.

Conclusion

Swabbing agar plates is a simple yet powerful technique to isolate, preserve, and expand mushroom cultures. With practice, you can maintain a clean and diverse culture library, experiment with rare strains, and ensure your mushroom cultivation projects thrive.

By following proper sterile technique and monitoring growth carefully, even beginners can successfully create healthy agar plates using swabs.

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