Photo by Billy Stone
The 2006 New Mexico mushroom season came to an interesting end with the appearance in mid-September of these odd little organisms (above) in the grassland around our home near Ribera, NM. They popped up just like regular mushrooms but they had no outer skin or membrane, no internal structure, or any other obvious means of holding themselves together. They just look like dark little balls of dirt. They crumble into a kind of oily dust between your fingers when they're dry (which they usually are, around here) and they're kind of spongy-crumbly, like cake, when they're wet. They didn't seem to "fit" anywhere in any of the usual mushroom literature, and had my mycological friends and me scratching our heads wondering what they were.
Intrepid NMMS member Ted Stampfer finally asked Dr. Jim Trappe of Oregon State University, the North American expert on truffles and other things hypogeous (belowground), who suggested that they might belong to the recently-erected fungal Class Glomeromycetes, which are known as Arbuscular Mycorrhizal Fungi or AMF (sometimes also called Vesicular-Arbuscular Mycorrhizae or VAM), fungi that form symbiotic associations with most plants. We sent him some specimens and thus began the communication below.
November 25, 2006 - This in from Dr. Trappe:
Your mystery fungus is Acaulospora sporocarpia Berch, originally described in 1985 by Shannon Berch (Mycotaxon 23: 409-418) from Arizona 70 mi. S. of Winslow but also known from one collection from Pakistan. The Pakistan material, however, differs in several ways and probably should be a different species. I have never seen this species until your specimens arrived here. It evidently is a species of arid lands and is rarely collected (but it may be common but overlooked...keep your eagle eyes open for more).
I'm sending 2 of the specimens you sent to me to Dr. Chris Walker in England, the world authority on this and related genera. He will try to establish it in pot culture with a host plant and will send some to Dr. Arthur Schüßler of Germany for DNA sequencing.
Thanks very much for contacting me about this find; I'll be keen to see any other hypogeous fungi you encounter, because not many collections have been made in New Mexico, but it must surely have plenty of species, many unusual or new.
November 27, 2006 - This arrived from Dr. Chris Walker:
I am rather excited about your find of Acaulospora sporocarpia (shows what a sad life we taxonomists live). This fungus is so unlike any other in the group that I really never quite believed the original description. I don't know how much chance there will be of establishing a culture (if it is really an Acaulospora, it will have to be grown with a plant). However, nothing ventured, nothing gained, as they say. Providing the material is not too old and dry, there may, however, be a good chance of extracting DNA, and I will send some away as soon as I can to my colleage in Germany.
December 05, 2006 - More from Dr. Walker:
As to why I was so excited about your Acaulospora sporocarpia (assuming that is what it is), this is because the only other record I am aware of is the original collection...so, yours, I think, is only the second time this organism has been collected. It is the only material that has any chance of still being alive, and therefore is very important indeed. You will perhaps see from our website that we are working on the phylogeny of these organisms to try to establish the natural relationships amongst them. I am hoping that your specimen will answer the question of whether or not A. sporocarpia really belongs to the genus. As far as I know, it is the only sporocarpic member of the entire order, and it therefore raises my suspicions.
March 09, 2007 - Dr. Walker reports:
I have a preliminary report back from my colleagues in Munich, and the first assessment places it in the correct group with the Acaulospora spp. So, we await a more detailed phylogenetic analysis, but at least we can be fairly sure now that we do indeed have an arbuscular mycorrhizal fungus. They also report that their Plantago pot culture, 'seeded' with your spores, is growing better than anticipated, which suggests maybe a successful mycorrhiza establishment. Of course, we will have to wait until the roots have been cleared. I won't touch mine until the full three months are up, as I like to leave them undisturbed as long as possible. Some species are a bit sensitive to mechanical disruption.
April 12, 2007 - Another report:
...we have so far had very disappointing results from our pot culturing efforts. I have checked two culture attempts in UK, and two in Germany, and none has come up with any indication of mycorrhizas. Usually after 3 months, things are going strong if they are going to work at all. However, I am going to leave them at least another month and have another look. Perhaps the warmer weather will start them off. Maybe they are host-specific, or perhaps they insist on having New Mexico or Arizona soil (the original collection is supposedly from Arizona, though I have some doubts as there is a place by the same name in New Mexico, and the guy who collected it lived near there. The collection was from 'a borrowed pit 40 miles SW of Winslow, Arizona', but they were collected by D J Stouffer, New Mexico, and there seems to be no data with the type except a hand written note from Jim Trappe made about 30 years later. All a bit mysterious, really!
June 01, 2007 - The latest report:
Not exciting news, I'm afraid. I was in Munich last week, and was able to talk to Herbert Stockinger, the man who is doing the DNA extraction work. The earlier assessment that the DNA was probably from the Acaulospora clade has turned out to be erroneous. Apparently further investigation showed the result to be an error, possibly due to contamination, as it also showed a common Glomus species too, and this cannot be if the DNA was uncontaminated. So, it is back to the drawing board in this regard. I have to extract some more spores from the sample and send them for another try.
Somewhat confusing news in regard to the pot culture attempts. There is not even the slightest hint of mycorrhiza present in most of the cultures we have tried so far. Mauritz Vestberg in Finland is having another try. He is going to (probably already has done) deep freeze the spores for a period and try again. One of my cultures, examined this morning, actually has colonisation, but it looks like an 'ordinary' Glomus, rather than anything more spectactular. This is a puzzle, since I did not find any Glomus in the original material. On the other hand, I have experience of producing more than one species from a 'sporocarp' that apparently has only one kind of spore, probably from a bit of viable mycelium intertwined amongst the spores. It is just possible that A. sporocarpia has a glomus-like phase. There were no spores yet in the substrate -- only in the roots -- so more time is needed.
Well, we are in it for the long-haul, as they say. So I will keep plugging away. Here's an idea. Now that your Bouteloua will be growing nicely, dig some up, complete with roots, and very thoroughly wash away all the soil and any attached decaying vegetation. Then plant them up in pots containing sterilised substrate (you can sterilise some of your local soil in a microwave). After some months (at least 3) we can then see what has sporulated in the substrate, and also see what is in the roots by staining).
Sorry for all this doom and gloom. I had hoped we would have it all well sorted out by now, but this is the nature of research into AMF. Quite a lot of things have taken me more than a decade to sort out.
Habitat: Solitary to scattered, occasionally two found contiguous or conjoined, in open, sandy, predominantly blue grama (Bouteloua gracilis) grassland soil (pH=7.3 +/-) in pi¤on/juniper woodlands, up to 10 meters ouside of tree drip-line. Not noticed inside drip-line. Fruitbody forming cracked "mushrump" in soil, not extending more than 1-2 cm above edge of crack. Cracked soil settling down around fruitbody with rain, leaving fruitbody partially to fully exposed on the soil surface. Fruitbody persistent, slowly weathering down over time.
Description: Width: 1-2.5 cm, roughly round. Height: 1.5-3.5 cm, generally tapering, sometimes narrowly, to base. Fruitbody surface encrusted with soil, sometimes showing some pitting, no exterior membrane/peridium. Crumbly with an oily, moss-like feel when dry, spongy when wet. Odor similar to linseed oil noticed after being enclosed in container. Interior blackish to reddish brown, apparently composed of sand and soil bound together with undifferentiated cellular network. When viewed with hand lens, hyphae protruding from surface, giving it a slightly velvety appearance, and shiny black spheres visible throughout interior. No visible columella or chambering.
Dr. Trappe sent us to Dr. Tom Bruns' website at UC Berkeley so we could download his 1974 article written with Dr. J.W. Gerdemann on
The Endogonaceae in the Pacific Northwest (15-mb pdf file), in which the genus Acaulospora is first described.
A really nice place to learn more about AM fungi is at Dr. Janusz Blaszkowski's website from the University of Agriculture in Szczecin, Poland.
Here's some food for thought...
"The study of plants without their mycorrhizas is the study of artefacts.
The majority of plants, strictly speaking, do not have roots; they have mycorrhizas."BEG Committee, 25th May, 1993
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