One Fungus = One Name: Fungal Nomenclature in the Age of Genetic Analysis

A few weeks ago Mark got a call from a person who was wondering why a fungus that we work with, he believes it was Zythia ,also has another name, that being Gnomonia.

There's quite a bit to sort out here, and so please follow us here.

This is a topic very much worth some discussion as renaming of things in our day does carry some emotional weight to it, indeed Mark suspects this person was wondering if these two names weren't part of such a scheme.  As any bird watcher knows, the birder community has been rocked in recent times by the plan of the American Ornithological Society to rename some 80 birds because the current names are seen as offensive by some (which we are not going to publicize here).

The double naming, also known as "dual nomenclature", of many fungi, which refers to sexual and asexual stages of the same fungus, is nothing like this however.  The way this system of two names for the same fungus came about was that the botanist Karl Linnaeus, who in the 18th century began to formalize the system of naming organisms, saw fungi simply as plants and concluded from there that fungal spores were like seeds.  And so it followed, in the mind of Linnaeus, that since one species of plant equaled one single type of seed, it would only follow that one species of fungus should equal one type of spore.  The problem that we now know is that the asexual form,  the anamorph, of many fungi looks one way and produces one kind of spore, while the sexual type, the teleomorph, of the very same fungus is totally different and produces an entirely different type of spore.

Put another way, the changing of the shape or form, biological function and reproductive methods (think sexual vs asexual) of the same fungus is usually driven by environmental cues and is what has resulted in the dual nature of fungal naming, simply because scientists until recent times saw them, naturally since the two forms didn't look anything like one another, as different fungi.

So still for many fungi the asexual stage and the sexual stage have different names, although the fungus is the same one. For the field practitioner, a lot of this doesn't make a huge difference, since most of the fungi we deal with and see out in the field like Botrytis gray mold, powdery mildew and anthracnose are in the anamorph stage, although it is worth noting that they do have a teleomorphic stage as well - Botrytis has Botryotinia fuckeliana (see photo below, it has not yet found in California, although every once in a there are rumors), Colletotrichum which causes anthracnose has Glomerella, and Zythia is the anamorph of Gnomonia. Powdery mildew, Podosphaera aphanis, of strawberry and raspberry, has made the transition to one name only for both the asexual and the sexual stage.

Speaking of Podosphaera aphanis, you might see it having another name, syn, Sphaerotheca macularis. It is a different story from the above.  Sphaerotheca macularis is the former name of Podosphaera aphanis. You might see it used in some older literature. The name change was due to new genetic tools used for taxonomy. This blog post explains it in more detail (https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=4260).

What has been bringing the story of dual nomenclature nearer to a close - and yes there is plenty of controversy in between - is the use of the use of genetic analysis which allows for the close view of to confirm that these to our human eye differently formed versions of the same fungus are indeed the same.

 

 

Botryotinia fuckeliana on the left (produced in the laboratory), Botrytis cinerea on the right (a mummified strawberry).

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