#087: Gymnosporangium juniperi-virginianae, Cedar-Apple Rust

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8 Responses

  1. Anna Elizabeth Henning says:

    Hi there! Question- is the gall the fruitbody of the fungus in this case, or is the gall produced by the tree, and in that case, is the gall considered more tree, or more fungus?

    • Thomas Roehl says:

      Good question – the gall is a little bit of both. Most of the tissue in the gall consists of plant cells. However, the fungus is growing through and feeding on the plant tissue. Without the fungus, the gall isn’t produced, so you need both fungal and plant cells to make a gall. The gall is mostly plant, but part fungus. However, the gall is not a fruitbody. For G. juniperi-virginianae, the fruitbody is the orange tentacles that grow out of the gall.

      • Anna Elizabeth Henning says:

        Thank you for your reply, Thomas! I have a gall on hand and am experimenting with it. So it would be correct to say that the gall is essentially the tree, but is parasitized or colonized by the fungus?

      • Anna Elizabeth Henning says:

        So, similar to the sclerotia associated with Inonotus obliquus, then. Thanks again! Do you have an instagram?

        • Thomas Roehl says:

          That’s right. Although, chaga is not a sclerotium (the structure and function are different). I do not have an Instagram (not yet, anyway).

          • Anna Elizabeth Henning says:

            Oh, interesting- the prevailing name for the growth in what I’ve read has been ‘sclerotia’. This is the term in the scientific papers I’ve seen as well as on Michael Kuo’s site. What would you call it? What is different about it from what you understand as sclerotium?

          • Thomas Roehl says:

            You’re right — ignore what I said. Sclerotium isn’t very well defined, so I probably use it in a more limited scope than most mycologists. The typical sclerotium is a knot of fungal tissue that stores food, usually to help the fungus overwinter. For a good example of typical sclerotia, see Hypholoma tuberosum. Morels make a structure with the same function, but it is actually a pseudosclerotium because it incorporates debris. Claviceps purpurea produces above-ground sclerotia that are a mix of fungal and plant tissue and are critical for overwintering. Chaga has a more irregular shape than typical sclerotia and isn’t enclosed by a hard rind on all sides (usually a requirement to be a sclerotium). Additionally, we don’t know its purpose: food storage might fit the definition, but if it’s primarily for gas exchange or toxin disposal it wouldn’t fit the definition. The structure is too messy and we we don’t know enough about its role, so I don’t like calling chaga a sclerotium. Instead, I use the non-scientific names “conk” or “clinker.” Personally, I think that since morels make pseudosclerotia, we should also have a specific term for sclerotia that include plant tissue and another term for chaga-like sclerotia. But my opinion doesn’t count for much, so use the terms you find in published research.

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