Agar medium is a solid gel-like substance that is made from seaweed extract and contains nutrients and water for fungal growth. Agar medium is commonly used in mushroom cultivation to germinate spores, isolate pure cultures, clone mushrooms, and store cultures for long-term preservation.
Germinating spores on agar medium is a useful technique that allows you to start your mushroom cultivation journey from scratch. By germinating spores on agar medium, you can observe the growth of mycelium (the vegetative part of fungi) and select the best strains for further expansion. You can also identify and eliminate any contaminants or competitors that may be present in your spores.
In this blog post, I will show you how to germinate spores on agar medium in a simple and effective way. You will need some basic equipment and materials, as well as a sterile and clean working environment. You will also need some patience and attention to detail, as germinating spores on agar medium can take anywhere from a few days to a few weeks.
What You Will Need
- Spores: Spores are the reproductive units of fungi that can grow into new mycelium. Spores can be obtained in different forms, such as spore prints, spore syringes, or spore swabs. Spore prints are collections of spores that are deposited directly from a mushroom onto a surface, such as foil or paper. Spore syringes are liquid solutions that contain spores suspended in sterile water. Spore swabs are cotton swabs that have been rubbed on a spore print or a mushroom gill.
- Agar medium: Agar medium is a solid gel-like substance that is made from seaweed extract and contains nutrients and water for fungal growth. Agar medium can be purchased ready-made or prepared at home. To prepare agar medium at home, you will need agar powder, malt extract powder, distilled water, and a heat-resistant flask or jar. You can also add other ingredients to your agar medium, such as peptone, yeast extract, or antibiotics, depending on your preference and purpose.
- Petri dishes: Petri dishes are shallow circular containers that are used to hold agar medium and cultures. Petri dishes can be made of glass or plastic and can be purchased sterile or non-sterile. Sterile petri dishes are preferable for germinating spores on agar medium, as they reduce the risk of contamination. However, non-sterile petri dishes can also be used if they are sterilized before use.
- Pressure cooker or autoclave: A pressure cooker or autoclave is a device that uses high temperature and pressure to sterilize materials and kill any living organisms. A pressure cooker or autoclave is essential for germinating spores on agar medium, as it ensures that the agar medium and the petri dishes are free of any contaminants or competitors that can harm or outgrow the mycelium.
- Still air box or laminar flow hood: A still air box or laminar flow hood is a device that provides a clean and sterile working environment for germinating spores on agar medium. A still air box is a simple box with arm holes that prevents air currents from disturbing the work area. A laminar flow hood is a more advanced device that filters and blows sterile air over the work area. A still air box or laminar flow hood is optional but highly recommended for germinating spores on agar medium, as it reduces the chance of contamination from airborne particles.
- Alcohol lamp or lighter: An alcohol lamp or lighter is a device that produces a flame that can be used to sterilize tools and materials. An alcohol lamp or lighter is necessary for germinating spores on agar medium, as it ensures that the needle or scalpel that is used to inoculate the agar medium with spores is free of any contaminants or competitors that can harm or outgrow the mycelium.
- Needle or scalpel: A needle or scalpel is a tool that is used to inoculate the agar medium with spores. A needle can be attached to a syringe that contains spore solution or liquid culture. A scalpel can be used to cut out a piece of agar that contains mycelium from another petri dish. A needle or scalpel must be sterilized before use by flaming it until it glows red and letting it cool slightly.
- Gloves and mask: Gloves and mask are personal protective equipment that can help prevent contamination and infection. Gloves and mask are advisable for germinating spores on agar medium, as they protect your hands and face from touching or breathing in any contaminants or competitors that can harm or outgrow the mycelium.
How to Germinate Spores on Agar Medium
- Prepare your agar medium. If you are using ready-made agar medium, skip this step. If you are making your own agar medium, measure the desired amount of agar powder, malt extract powder, and distilled water according to the recipe you are using. For example, a common recipe is 15 grams of agar powder, 10 grams of malt extract powder, and 500 millilitres of distilled water. Mix the ingredients well in a heat-resistant flask or jar and cover the opening loosely with a lid or foil. Place the flask or jar in a pressure cooker or autoclave and sterilize it for 15 minutes at 15 psi. Let the pressure cooker or autoclave cool down naturally before opening it.
- Pour your agar medium into petri dishes. If you are using sterile petri dishes, skip this step. If you are using non-sterile petri dishes, place them in a pressure cooker or autoclave and sterilize them for 15 minutes at 15 psi. Let the pressure cooker or autoclave cool down naturally before opening it. Once your agar medium and your petri dishes are sterilized and cooled down, set up your still air box or laminar flow hood and work inside it. Shake your agar medium gently to mix it well and pour it into each petri dish until it covers about half of the dish. Do not fill the dish too much or too little, as this can affect the growth of the mycelium. Cover each dish with a lid and let the agar medium solidify completely.
- Inoculate your agar medium with spores. Depending on the form of spores you are using, you will need a different method of inoculation. If you are using a spore print, cut out a small piece of foil that contains spores with a sterile scalpel and place it on top of the agar medium in the center of the dish. Cover the dish with a lid and tape it shut. If you are using a spore syringe, shake it well to distribute the spores evenly in the liquid and wipe the needle with an alcohol wipe. Flame the needle until it glows red and let it cool slightly. Insert the needle through the lid of the dish and inject a drop of spore solution onto the agar medium in the center of the dish. Withdraw the needle and tape the hole shut. If you are using a spore swab, wipe it with an alcohol wipe and flame it until it glows red. Let it cool slightly and rub it gently on the agar medium in a zigzag pattern across the dish. Cover the dish with a lid and tape it shut.
- Incubate your inoculated agar medium. Label each dish with the date and strain name and store them in a dark place at room temperature (about 20-25°C) for 2-4 weeks until you see white mycelium growing from the spores. Check your dishes regularly for any signs of contamination or competitors, such as mold, bacteria, yeast, or insects. If you see any contamination or competitors, discard the dish immediately and do not use it for further cultivation.
- Transfer your colonized agar medium to new dishes or substrates. Once your agar medium is fully colonized by mycelium, you can transfer it to new dishes or substrates for further expansion or fruiting. To transfer to new dishes, cut out a small piece of colonized agar with a sterile scalpel and place it on top of fresh agar medium in a new dish. Cover the dish with a lid and tape it shut. To transfer to substrates, break up some colonized grains with your hands or a spoon and mix them with moistened substrates (such as straw or sawdust) in a bag or container.
Congratulations! You have just germinated spores on agar medium and started your mushroom cultivation journey from scratch. You can now enjoy the process of growing your own mushrooms from mycelium.
I hope you enjoyed this blog post and learned something new about germinating spores on agar medium. If you have any questions or comments, please feel free to leave them below. Happy mushroom growing!
