Sporing Mushrooms: A Step-By-Step Guide To Spore Testing

With tens of thousands of mushroom species in the world, only a few are edible and delicious, such as Portobello, oyster, and chanterelle. Knowing how to spore test a mushroom is crucial for identifying and differentiating between the edible and non-edible varieties. Spore testing involves examining the gills or creating a spore print by placing the cap on paper or another firm surface overnight. The spores, which come in a variety of colours, will leave a coloured print that can be used, along with field guides and online research, to identify the mushroom species.

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Spore printing techniques

Spore printing is an accessible technique for identifying mushrooms and is considered a crucial step in correctly identifying mushrooms. It is also used for studying allergens or pathogens linked to fungi and for cooking enthusiasts to identify edible mushrooms.

Selecting the Mushroom

Select a mature mushroom with a cap that has gills or pores. The mushroom should be fresh and soft, as hard mushrooms will be more difficult to obtain spore prints from. If the mushroom is young, it may have a "veil" covering the gills, protecting them during development.

Preparing the Mushroom

Carefully remove the mushroom cap from the stem at the highest possible point. If you have a shelf mushroom or an oyster-type mushroom, you may be able to use the whole mushroom.

Preparing the Surface

Place the cap of the mushroom, gill or pore-side down, on a piece of paper, tinfoil, aluminium foil, a glass microscope slide, or a black plate. Using black paper can help the print show up, but for identification purposes, you may also want to use white paper, as some mushrooms have white spores. If you plan on growing the mushrooms from the spores, it is better to use tinfoil or glass as it is more sterile and easier to scrape spores from.

Capturing the Spores

Cover the mushroom cap with a bowl, cup, or glass and leave it for 2-24 hours, depending on the humidity and the freshness of the mushroom. The spores will fall onto the surface, creating a spore print pattern. If you only have a portion of the cap, or if the mushroom has pores, add a drop of water to the cap to help release the spores.

Preserving the Spore Print

To preserve the spore print, fold the paper or tinfoil and store it in a ziploc bag. Label the spores with the date and type of mushroom. Spore prints can be stored at room temperature and will last for decades. To fix the spores permanently, you can use artist "fixative" or hair spray, holding the spray at least 12-15 inches above the print.

Using microscopy to identify spores

Microscopy is a useful technique for identifying mushroom spores. It involves using a microscope to study objects that are too small to be seen by the human eye. Mushroom spores are very small and can only be seen individually with a microscope. With the correct technique, microscopy allows us to visualise, identify, measure, and photograph spores.

To study mushroom spores using microscopy, you will need to collect spores onto a slide. One way to do this is to cut off the stem of a mushroom, place the cap on a glass microscope slide with the underside facing down, and cover it to keep out drafts. Leave it overnight, and the cap will drop its spores onto the slide. Alternatively, you can scrape spores from a spore print onto a slide. A spore print is made by placing the mushroom cap on a sheet of paper or foil and covering it, so the spores fall onto the surface and form a spore print pattern.

Once you have spores on a slide, place the slide on the microscope stage and start with low magnification. Spores are very small, so you will need to move through progressively higher magnifications, bringing the spores into focus each time. When using high magnification, an oil-immersion lens and a drop of immersion oil on the coverslip may be necessary. Use the fine-focus knob to make final adjustments and bring the spores into clear view.

To identify mushroom species, it is essential to determine whether the spores are amyloid, inamyloid, or dextrinoid. This can be done using Melzer's reagent, which contains chloral hydrate, water, iodine, and potassium iodide. Amyloid spores turn blue-black, dextrinoid spores turn reddish-brown, and inamyloid spores turn yellowish or show no change. Iodine also reacts with starch to produce a blue-black colour, so the colour reaction of mushroom surfaces to KOH can also aid identification.

How to identify edible mushrooms

Identifying edible mushrooms can be a tricky task, and it is strongly advised that you do not eat a mushroom unless you are 100% sure it is edible. If you do eat an unidentified mushroom and experience symptoms such as gastrointestinal upset, seek immediate medical treatment.

To identify edible mushrooms, it is important to learn about the different types of mushrooms and their characteristics. This can be done through field guides, books, online forums, or by consulting experts. Here are some general guidelines to help you identify edible mushrooms:

• Edible mushrooms typically have brown or tan gills, while mushrooms with white gills are often deadly.
• Choose mushrooms with tan, brown, or white caps and stems rather than red.
• Edible mushrooms usually do not have scales on the cap or a ring around the stem.
• Avoid mushrooms with a skirt or ring on the stem and a bulbous or sack-like base called a volva.
• Learn to identify mushroom families such as Agarics, Boletes, Milkcaps, Russulas, and Amanitas, as each family has unique characteristics that can help you determine edibility.
• Some mushrooms, like Puffballs and Chicken of the Woods, are relatively easy to identify and are considered safe options.
• Morels are edible, but there are also false morels that can be dangerous, so proper identification is crucial.
• When foraging, take two baskets. Place mushrooms you are confident are edible in one and those you are unsure about in the other.

While these guidelines provide a basic understanding of identifying edible mushrooms, it is important to consult reliable sources and experts for more detailed information. Mushroom identification can be complex, and your safety should always be the top priority.

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Environmental influences on spore production

Mushrooms produce spores to spread and find new food sources, but also to create new strains and ensure the survival of the species. The spores are dispersed in a two-phase process: first, they are ejected from the gill surface by surface tension catapults, and then they are carried by the wind currents in the surrounding environment. Mushrooms also use convectively created airflows to disperse spores, which is particularly useful when they grow in obstructed environments, such as close to the ground or crowded together. The rapid water loss from the pileus enables mushrooms to create convective cells for dispersing spores.

Spores are typically less than 10 μm in size and are extremely lightweight, allowing them to be carried by wind currents. However, wind speed and direction can vary, and mushrooms have evolved to influence spore dispersal even in low-wind environments. Water vapor loss creates slow airflows that carry spores out from under the mushroom cap. Additionally, mushrooms growing in close proximity can enhance spore dispersal by providing boundaries for the upward-flowing air currents to climb.

Environmental conditions such as temperature, humidity, and the presence of moisture play a crucial role in spore germination. Spores require a suitable food source, typically decaying organic material, to germinate and grow into new mushrooms. They can remain dormant until the environmental conditions are optimal for growth.

While mushroom spores are generally harmless in small amounts, repeated exposure to large volumes of spores can be dangerous and cause allergic reactions. Oyster and shiitake mushrooms, for example, produce a significant number of spores, and it is recommended to harvest them before they release their spores.

Spore print preservation

Spore prints are the easiest to reseal and store for later use. To preserve a spore print, you must first allow the spores to air dry for 30 to 60 minutes to remove any remaining moisture. Then, you can cover the spore print with a transparent sheet, such as plastic wrap, or place it in a mycology notebook. Alternatively, you can use artist "fixative" (or simply hair spray) to "fix" the spores permanently. Just be sure to hold the spray at least 12 to 15 inches above the print, or you may blow the spores off the paper.

Once you have a spore print, it is recommended that you keep it sealed in its original packaging until you are ready to use it. When storing your spore print, it is best to keep it in a room that does not vary widely in temperature. If temperatures get too hot or too cold, it may damage the spores. Try to keep your spores between 36 and 75 degrees Fahrenheit. Additionally, rooms that have doors leading to the outdoors are more likely to vary in temperature and may be more prone to contaminants. It is recommended to keep your spores away from exterior walls or windows where fluctuations in temperature are greater. From there, you can place your sealed container in a cool, dark place away from direct sunlight. Cabinets, closets, or drawers are great spots to store your spores. Make sure to label your spore print with the date and type of mushroom so you can easily identify them later.

Spores are quite resilient and can survive in many environments, including space! With proper storage, spore prints can last for decades and still remain viable for microscopy research. In fact, a laboratory case of spore germination is known to have occurred after 20 years of storage.

Frequently asked questions