How to Use Agar to Clone Mushrooms: A Step-by-Step Guide

Agar is a powerful medium for mushroom growers—it’s used not only to propagate spores but also to clone mushrooms from existing fruit bodies. Cloning mushrooms allows you to replicate the exact genetics of a mushroom that you like, preserving desirable traits such as taste, size, or speed of growth. In this article, you’ll learn how to clone mushrooms using agar and how to cultivate the perfect mycelial culture.

Why Clone Mushrooms on Agar?

Cloning mushrooms allows you to skip the unpredictable spore germination process and ensure consistent results. Agar provides a nutrient-rich medium that helps mycelium grow rapidly while also allowing you to easily identify contamination, making it the perfect tool for isolating strong genetics.

Tools and Materials Needed

• Petri Dishes: Sterile plastic or glass petri dishes.

• Agar Medium: A typical recipe for mushroom agar is 10 grams of agar powder, 10 grams of malt extract, and 500 mL of water.

• Scalpel: Sterilized for cutting mushroom tissue.

• Alcohol Lamp or Bunsen Burner: To create a sterile flame.

• Mushroom Sample: A healthy, freshly harvested mushroom.

Step 1: Prepare the Agar

1. Mix and Sterilize:

   • Mix 10 grams of agar powder, 10 grams of malt extract, and 500 mL of water. Stir thoroughly to dissolve the agar and malt extract.

   • Pour the solution into a jar or bottle suitable for sterilization.

   • Sterilize the agar in a pressure cooker at 15 PSI for 20 minutes to eliminate any potential contaminants.

2. Pour Agar into Petri Dishes:

   • Once the agar has cooled to around 50-55°C (but before it begins to solidify), pour it into petri dishes in a sterile environment. Pour about half a centimeter deep.

   • Let the plates cool and solidify completely before moving on.

Step 2: Prepare for Cloning

1. Select a Mushroom for Cloning:

   • Choose a healthy, mature mushroom. For best results, select a mushroom that has desirable traits—such as fast growth, large size, or a great taste profile.

2. Set Up a Sterile Environment:

   • Work in a still air box (SAB) or under a laminar flow hood. Sterilize all tools, your hands, and the workspace using 70% isopropyl alcohol.

Step 3: Transfer Mushroom Tissue to Agar

1. Open the Mushroom:

   • Tear the mushroom open by hand to expose the inside. Avoid cutting the mushroom with a knife, as this can drag contaminants from the outer surface into the internal tissue.

2. Take a Tissue Sample:

   • Using a sterilized scalpel, take a small piece of tissue from the inner stipe (the stem) or cap. This tissue should be pure and free from contamination.

   • Quickly transfer the tissue to the center of an agar plate, placing it gently onto the agar surface without pressing it in.

Step 4: Incubate the Agar Plates

1. Seal and Store:

   • Seal the petri dish with parafilm or plastic wrap to prevent contaminants from entering.

   • Place the plates in a warm, dark environment with temperatures between 21-25°C. After about 5-7 days, you should see mycelium growing out from the tissue sample.

2. Monitor Growth:

   • Check the plates daily for signs of contamination. Mold typically appears as green, black, or other discolored patches.

   • If the mycelium grows healthily (bright white and fluffy), it’s ready for further use. If contamination appears, isolate uncontaminated sections on a new agar plate by cutting them out and transferring them.

Step 5: Transfer Healthy Mycelium to Grain Spawn

Once you have a healthy agar culture, it’s time to expand it onto a grain substrate:

1. Prepare Grain Spawn: Sterilize grain in jars as described in the grain spawn preparation article.

2. Inoculate Grain with Agar:

   • In a sterile environment, use a sterilized scalpel to cut a small piece of healthy mycelium from the agar plate and drop it into a sterilized jar of grain.

   • Seal the jar and store it in warm, dark conditions. Within 2-3 weeks, the mycelium should fully colonize the grain, making it ready for bulk substrate inoculation.

Conclusion: The Benefits of Cloning Mushrooms Using Agar

Cloning mushrooms using agar is a powerful tool for mushroom growers. It allows you to create consistent crops, expand the best traits, and rapidly scale up your growing efforts. Agar techniques may seem intimidating at first, but once mastered, they open up countless possibilities for selecting and propagating the most vigorous strains. Start experimenting, and soon you’ll have your own library of cloned cultures ready for any growing project!