This quick update will cover our recent project with Dr. Rytas Vilgalys, Professor of Biology at Duke University. Dr. Rytas was kind enough to do some PCR DNA and get an ITS sequence of some of our various collections of Pleurotus that were found growing on pine wood.
Over the past 2 years, James and I have been on the hunt for an oyster mushroom that grows on pine. To explain, I should first give a little background about these particular fungi. They tend to favor deciduous wood, especially poplar trees in Colorado. To most fungi, pine wood isn’t something easy to eat. Coniferous trees contain natural resins that tend to contain chemicals that are quite anti-fungal. This does not mean that fungi cannot eat coniferous wood, it is just quite difficult for them to do. However, Pleurotus are special fungi. They have discovered a quite efficient method of decomposing their substrate, excreting powerful digestive enzymes able to breakdown many different types of freshly cut wood. There is even a type of Pleurotus that can grow on cactus skeletons! The Pleurotus that James and I had found were growing from the cut stumps of pine trees and a spruce log growing at 10,000′ in elevation. These were cultured in our lab in Denver and were eventually sent to Dr. Rytas. He was interested in them because of their unique habitats they were found growing in and was wondering, as we were, if they were a possible new species of Pleurotus. He also received a few control collections of Pleurotus pulmonarius from various locations in the state, growing from cottonwood trees. These were tested against the mushrooms that were found growing on conifers. This testing is basically done by taking known sets of genes from a specific species of fungi and testing samples of DNA against those genes to see if they are similar enough to be the same genetic group (hopefully that wasn’t too over simplified?). Much to our surprise, every specimen came back as P. pulmonarius! It is well documented that P. pulmonarius grows occasionally from conifer, but these specimens also had unique morphological features that were distinctly different, even with indoor grown mushrooms in a controlled environment! Just goes to show that morphology sometimes can tell you very little about what type of fungi you have. We now know that our cultures of oysters collected from these conifer habitats are P. pulmonarius, but have somehow developed a unique set of digestive enzymes to deal with the oils in the wood that tend to inhibit fungi.
The reason James and I are extremely interested in pine loving oysters is because the Rocky Mountains are plagued with a pine eating beetle that is destroying our forests by the entire mountainside. The general way to deal with this problem (due to the extreme fire danger it creates) is to cut down the infected trees and pile them in large piles. They are used mainly for fire wood, but the pine loving mushrooms would decompose the wood much faster, creating larger soil depth. Paul Stamets has a discussion in his book, Mycelium Running, about the honey mushroom and its method of creating a deeper humus depth. Many of these plagues, whether they be a fungus or an insect, may look very disastrous to the environment to humans. This is only because of our perception of time. The trees that once stood as a forest are now decomposing, increasing the potential of the forest to create more life. As soil depth increases, the forest can house more and more plants. We would like to make these Pleurotus part of the solution to this large problem we are facing today.