Genomics project targets mushrooms

University of Alaska researchers ask that pickers share their info

Posted: Monday, July 04, 2005

FAIRBANKS - If you haven't found many dollars worth of morel mushrooms this season, there remains at least some possibility that you could at least receive a little credit.

Scientific credit, that is.

Biologists studying mushrooms and other fungi for the Fungal Genomics Project at the University of Alaska Fairbanks would appreciate it if mushroom pickers shared with them a mushroom cap or two - especially the most unusual looking fungi of their harvests.

There are nine known subspecies of morel mushrooms, not all of which occur in Alaska, said Gary Laursen, a senior research biologist with the Institute of Arctic Biology. There are two species of black morel, the most common and popular fruit in this state. But there may be more. No one knows for sure because a true scientific taxonomy of Alaska mushrooms has yet to be completed.

Alaskans may have been sautéing a whole new variety of morel mushroom for years and not known it. That's not to say it would matter for the skillet. Laursen and four colleagues are focusing on fungi specifics beyond the common names that most fry cooks would care about.

"Common names tend to cluster what we as taxonomists might put into two or three different species," Laursen said.

He and others connected with the mycological herbarium at UAF are examining and describing all varieties of Alaska fungus for the project. Broader public interest in mushrooms this summer - given the possibility of commercial quantities of morel mushrooms popping up after millions of acres of Alaska's Interior forests burned last year - means a chance for the scientists to, perhaps, land an interesting specimen or two.

As Laursen put it in terms of hunting mushrooms in general, "the more eyes you have in the woods the more you find."

The scientists aren't concerned about collecting a great number of mushrooms from people. "We just need a cap or two," he said. "It can be fresh or dried."

As incentive, Laursen noted that this is a scientific first for Alaska and those whose mushrooms are found useful in the study would be listed as contributors in documentation of the project. "We like to get people's names," he said. "They're given credit in publications."

Looking closely at sponge-like morels, the surface looks like a field of pits and ridges. The mushrooms are called "cup" fungi because the pits on their surface serve as cups where spores are produced. One species may be all brown, one may have brown pits and white ridges, one might have white pits and brown ridges. The combinations are endless in grays, yellows and variations of color and shape. "There are a lot of subtleties that a taxonomist would use to delineate a species," he said.

The scientists not only look at the shape, color and size of the mushrooms, they consider where individual fruits grow and do microscopic and chemical tests on the fungi as well. Microscopic views look at the individual spores, of which a single mushroom might produce billions, and the cell makeup of the stem, cap and other parts of the fruit, Laursen said.

Chemical tests are then performed to sort out the RNA of the mushroom. RNA is half of the familiar helical DNA ladder that has become well known through television and movies. "Saw the ladder in half down the rungs and one half is the RNA," he said. The scientists actually focus on one small portion of the RNA as an identifier of mushroom species.

But, Laursen is quick to emphasize, the RNA finding is just one piece of the puzzle. "It's information to help delineate the species along with the macro and microscopic information," he said. "You have to look at the whole picture. It's not like DNA fingerprinting with humans."

The mushrooms are quite a puzzle for scientists, Laursen said. People know morels pop up after a fire, but exactly what nutrients are at work and in what quantity, what specific temperature and moisture combination is at work and even whether the mushrooms are specific to certain tree species - having a mycorrhizal relationship - is unknown, he said.

Trees could not grow around Fairbanks without the help of mycorrhizal relationships with fungus, he said. "Some have assumed morels are mycorrhizal, but it has not been documented," Laursen said.

To explain the relationship, Laursen described fungus as a sprawling web of fibers underground that digest nutrients in the soil. The mushrooms people see at the surface are the equivalent of fruit that appear only when conditions are just so.

Tree roots also seek nutrients from the soil, but Interior Alaska soil is so nutrient-poor that trees could not pull up enough nutrients on their own. What roots do have are sugars produced in photosynthesis by the tree. The fungi feed on the sugars, the trees feed on the nutrients pulled in by the fungi, and the symbiosis is complete.

Some mushrooms grow only with certain kinds of trees. Some scientists have speculated that morels have some sort of relationship with spruce trees, thus explaining the reason so many would pop to the surface when a spruce forest burns.

"The roots may still be alive under the surface," Laursen said. "But they're throwing out all their sugars in a last-ditch effort to survive. The morels may key on that and say, 'uh oh, we'd better do what we can,' and fruit in response to the tree being stressed."



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