Heterobasidion annosum - ability to enter roots?

Has anyone any information on how this fungus breaks down the thin bark of small roots. I.e. what chemicals it produces.

As part of an assignment I'm reading that it is categorized as an acitive pathogeneis due to its ability to enter roots under its own violition - but despite everything I've read (which is a lot:sneaky2:) I can't find evidence to explain this.

I could gloss over this in my answer, but now I'm getting intrigued.

I believe it transfers through root grafts, tree to tree, not sure if it can penetrate the root unaided.

Has anyone any information on how this fungus breaks down the thin bark of small roots. I.e. what chemicals it produces.

 

As part of an assignment I'm reading that it is categorized as an acitive pathogeneis due to its ability to enter roots under its own violition - but despite everything I've read (which is a lot:sneaky2:) I can't find evidence to explain this.

 

I could gloss over this in my answer, but now I'm getting intrigued.

I am halfway through "Modern Mycology", so I can guess at half an answer.

Fungi are limited in the complexity of chemicals they can produce to invade hosts. The limitation seems to be the passage of the chemicals through the cell wall of the fungla hypha. I culdn't prove it, but I think that suberized barriers (cork!) in bark is almost impenetrable by all but the most host-specific pathogenic fungi. What seems more likely is that H.a invades through unsuberized young root hairs or the smallest breaches in bark. If you were breaking into a house, you wouldn't go through the wall, you,d try all the windows and doors first. That kind of thing. Requiring a glasss-cutter rather than a jack hammer.

Fungi penetrate by secreting enzymes at the hyphal growth tip. The normally-insoluble cellulose can be defeated in this way. One typical group of enzymes I have read of are called glucoamylases. I thought these only acted to break down starches into sugars, but maybe they can do the same on cellulose.

Until someone comes along who knows what they are talking about, I'd say 'enzymes' and I'd also think windows, not walls. With H.a being known for cambium killing, an infection route under rather than through the bark seems likely, so starting at tiny roots before they get suberized, or by root grafts where no dense wall exists between touching trees.

If anyone can expand in this I'd be most interested.

Thanks Jules,

I'm being overly obsessive (anal) in attempting to find the answer. I don't believe that root grafts make it actively pathogenic - as it's not breaking/forcing entry (someone left the window open).

Be nice to identify the chemical process, but I think from what I read after posting, that you're on the right lines. Pearce has some interesting articles on RZ's and suberization - but most are to pay for.

I believe it transfers through root grafts, tree to tree, not sure if it can penetrate the root unaided.

Thanks Jules,

I'm being overly obsessive (anal) in attempting to find the answer. I don't believe that root grafts make it actively pathogenic - as it's not breaking/forcing entry (someone left the window open).

 

Be nice to identify the chemical process, but I think from what I read after posting, that you're on the right lines. Pearce has some interesting articles on RZ's and suberization - but most are to pay for.

Ah well, after discounting sapwood intact, sapwood exposed and heartwood as strategies, actively pathogenic is the only one left for H.a even if it's not strictly true.

You'll go crazy or bust trying to find the answer...

From my recent studies, few of these damn fungi want to fit into the categories that man wants to put them in. I'm starting to understand the fascination of the mycos among us

From my recent studies, few of these damn fungi want to fit into the categories that man wants to put them in. I'm starting to understand the fascination of the mycos among us

Exactly! Nature knows nothing of categories. Species evolve, niches are created, other species mutate and the successful mutants occupy the niche and thrive, becoming a new species. Definition boundaries mean nothing. Even the distinction between fungi and bacteria is pretty fuzzy. The boundary between fungi and the many many almost-fungi-but-can't-be-categorised stuff is completely arbitrary. Hardcore mycologists even turn their noses up at oomycota (e.g Phytopthora) because they have cellulose coats rather than chitin. More schisms than a church!

When I started learning about trees I wanted it to be simple and easily categorised but now that I have broken the back of it I crave exceptions to the rules and the ordinary becomes a little boring. You might become a closet myco yet. I feel myself being sucked in to the dark side. But like trees and fungi, I would settle for a symbiosis.

I'm going to have to have at what you're reading, I got defence mechanisms of woody plants- blanchette and Biggs, and fungal infection of plants by pegg and ayres today. Problem is time, all I get is to find the answers to assignments without reading everything. Next weeks a new unit and then it will something different to complete.

But saying that, I can now actually read fungal strategies and similar works and actually understand them. The pieces of the jigsaw are coming together, bit by bit

... I can now actually read fungal strategies and similar works and actually understand them. The pieces of the jigsaw are coming together, bit by bit

Isn't that a wonderful feeling? It started to sink into my brain on the third reading.

re your ?, Sinclair/Lyon say the fungal strategy is host-specific. But they are not as helpful as Schwarze re pathways.