(Arboricultural-styled) 'Fact of the Day'

[Kveldssanger]

27/12/15. Fact #109.

 

Some weeks ago I was asked to write a post on controlling parasitic Armillaria spp. colonisation, and did write up a response with some sourced material. I have however just come across something else, which is very interesting to say the least.

 

Sparassis crispa (the cauliflower fungus) and Armillaria spp. secrete the same antifungal and antibiotic compound (known as sparassol or orsenellic acid). Because fungi are resistant to their own secretions, if both aforementioned species of fungus exist within an area, neither will be affected by the compound. However, Sparassis crispa also secrets other antifungal compounds that can parasitise Armillaria spp.

 

What this means is that foresters may utilise Sparassis crispa - in the form of incoluating stumps with its spores - in regions peripheral to where Armillaria spp. are known to be blighting. This could potentially limit any Armillaria spp. spread, and reduce the financial impacts associated with timber damage upon a to-be-harvested forest.

 

Trametes versicolor may also readily out-compete Armillaria spp, for reasons associated with the rate of mycelial growth (turkey-tail will simply 'over-grow' honey fungus).

 

Source: Stamets, P. (2005) Mycelium Running. China: Ten Speed Press.

Edited December 27, 2015 by Kveldssanger

[sloth]

27/12/15. Fact #109.

 

However, Sparassis crispa also secrets other antifungal compounds that can parasitise Armillaria spp. .

 

All very interesting Sorry to 'nit pick', but could you clear this up for me please? Does the S crispa actually parasitise the Armillaria, or rather secrete antifungal compounds which affect the growth it?

Cheers...

[Kveldssanger]

The book says, and I quote:

 

"Cauliflower mushrooms (Sparassis crispa) secrete the antifungal antibiotic sparassol, or orsellinic acid, which is also produced by Armillaria fungi. Mushrooms are naturally immune to their own antifungal secretions and are unaffected by the same secretions from competitors. However, cauliflower mushrooms also secrete other antifungal agents that allow them to parasitize other Armillaria mushrooms. This suggests an antifungal strategy for foresters to consider. In principle, mushrooms like cauliflowers could defend forests against blights by Armillaria; innoculating stumps at the perimeter of an Armillaria blight could limit further spread of this destructuve forest disease."

 

So the answer is.... I don't know. I read it as the fungus parasitises Armillaria, in the sense that the compounds secreted attack Armillaria, making the existence of it alongside Sparassis crispa untenable.

 

The author shows how, when both are grown in the same pertri-dish, the cauliflower fungus will vastly outweigh the honey fungus in terms of capacity of the petri-dish occupied.

Edited December 27, 2015 by Kveldssanger

[sloth]

Interesting, not quite sure how to take that. I think of a parasite as taking nutrition in some form from its host, rather than preventing its biological functions to allow 'overgrowing' it.

Cheers for that...

[Kveldssanger]

Trametes 'overgrows' Armillaria by sheer exclusive rate of mycelial growth (it's a faster grower), though I don't think the author suggests Sparassis crispa 'overgrows' Armillaria, but instead suggests that compounds 'toxic' to Armillaria (secreted by Sparassis crispa) hinder growth of Armillaria.

 

Yes, perhaps the wrong use of the word by the author. Unless a Sparassis' antifungal compounds actually degrade the Armillaria, and the Sparassis then consumes the degraded Armillaria mycelium for its own use. But my understanding was that the Sparassis simply can amass a larger territory when combating Armillaria, by sheer virtue of its more expansive arsenal of antifungal secretions over and above sparassol.

Edited December 27, 2015 by Kveldssanger

[Kveldssanger]

I made a wordpress blog (so I can collate more of my stuff into one central area) - https://arboriculture.wordpress.com/

 

I will use this to document facts and other bits (such as pictures, and so on), though my facts will all be principally posted here for as long as I do post facts (which should be for a very long time), as will lots of cool snaps I take be posted here. I suppose it just gives stuff a wider audience perhaps, and as I will continually link back to here hopefully, if I do get any traffic, people will then visit here.

[daltontrees]

Interesting, not quite sure how to take that. I think of a parasite as taking nutrition in some form from its host, rather than preventing its biological functions to allow 'overgrowing' it.

Cheers for that...

 

I was a little confused too, it would be a new definition of parasitism.

 

The attached may help a little, if nothing else the general comments in the last paragrah of p.3 show that competition is fierce between fungi and that inhibition of other species including Armillaria is highly effective. Rather than being parasitism it is out-competition.

 

It also reads like sparassol and the similar ScI and ScII and orsenillic acid are not really synonymous. What I thought most interesting of all is that ScI and ScII are present naturally in woods, poresumably as antifungal defences, but that S. crispa can tolerate these better than its competitors can, giving it almost exclusive access to colonised (but still living) woody hosts.

 

It's a short step to assume that if ScI/II inhibits the opposition and S. crispa can produce it as can trees themselves, it would be a good way to contain other fungal spreads. What stops the S. crispa thereafter is another question.

scrispa.pdf

[Kveldssanger]

Great addition there. Shall read that later on. Cheers.

[Kveldssanger]

28/12/15. Fact #110.

 

Fagus sylvatica, once felled (or following death), can quickly become riddled with decay pockets. It is suspected that fungal endophyte species latently present within the tree's system, which cause no disease / decay symptoms during the host's life, are responsible for the rapid manifestation of decay following death. The exact entry of these endophytes in Fagus sylvatica is not largely understood, though it is anticipated that leaf scars, bud scale scars, the thin periderm, and lenticels are the main means of entry.

 

Laboratory experiments in the past have given weighting to such an assertion, when freshly-cut and healthy branches of Fagus sylvatica were incubated under varying drying regimes. After a period of 14 days, active mycelium could already be observed on the branches, indicating that latent endophytic fungi present at the time of the healthy branches being cut were the species now developing mycelial networks, and it is thought that the reduction in water content and increase of oxygen availability lead to the development of the mycelium (basically initiating the switch from latent to active).

 

Past studies had not shown that Fomes fomentarius, a very common white rot of Fagus sylvatica, could persist within healthy Fagus sylvatica for a period of time before the host's death (or detachment of a part of the tree), though the decay strategy adopted by Fomes fomentarius (in Fungal Strategies of Wood Decay in Trees, the authors here allege, though I cannot find a specific direct reference to this in the book asides from comments regarding colonisation of the xylem in living hosts) suggests that the species should be able to exist as an endophyte prior to the right conditions manifesting within the host. The reason for past studies not showing Fomes fomentarius as an endophyte may perhaps be because past studies looked only at branch wood, whereas Fomes fomentarius is known to principally colonise the main stem and larger limbs of its host.

 

In this study, therefore, samples were taken in February from the 'lower' canopy (diameter: 5-10cm), 'upper' canopy (diameter: 10-25cm), and main stem (diameter: 20-50cm), in order to test whether Fomes fomentarius does indeed exist within healthy wood. 360 main samples were taken from ten (outwardly) healthy Fagus sylvatica, all of which were 70-85 years old, once they had been felled, and then the samples were transported to a laboratory and processed within 24 hours into 2,160 smaller samples.

 

Once the 2,160 samples had been processed and incubated for the duration of the study (either 8, 16, or 24 weeks), mycelium observed to have grown from the samples were analysed, identified, and recorded. Of the 2,160 samples, 61 had mycelial growth of Fomes fomentarius. The table below shows the breakdown of how long it took for the mycelium to begin developing, and in what samples they were found (lower canopy, upper canopy, or stem).

 

 

What can be ascertained from these readings is that, whilst not a common endophyte (in these samples), Fomes fomentarius can indeed exist latently within a healthy Fagus sylvatica. Analysis of the locations of the samples also suggests that Fomes fomentarius will exist most frequently within the stem, much less frequently within the upper canopy, though not at all in the lower canopy. The data also indicates that Fomes fomentarius will not immediately begin its active mycelial phase following host death, but instead manifest after 16-24 weeks (or even longer, though this study ended after a 24 week period). A period of incubation is thus necessary, and active growth is likely initiated by a change in wood moisture content and the increase of oxygen (which may be the result of cracks associated with the drying wood).

 

The study did also address concerns regarding whether Fomes fomentarius presence was simply a result of contamination post-branch removal, and the authors suggest that because the samples were taken in February, before the sporulating season of the fungus (starting in March across Central Europe, where the study was done), contamination was unlikely. Additionally, because isolates were found growing within heartwood of the main stem and 'upper' canopy (where diameters of samples were over 10cm in diameter, and up to 50cm), it is unlikely that contamination would have caused this - if isolates were found in the xylem of the 'lower' canopy samples that were 5-10cm in diameter, contamination may have been possible. Furthermore, the location of the isolates correlates with the position of Fomes fomentarius sporophores, which are typically found on the main stem of the host. Lastly, all isolates of Fomes fomentarius were genetically different, which means contamination to such extents would have been very unlikely (particularly given the time of year).

 

Interestingly, the study also mentions that there has been evidence recorded by Danby, Boddy, & Lonsdale (but not published, it seems) of Fomes fomentarius being latently present within Betula pendula as well.

 

Source: Baum, S., Sieber, T., Schwarze, F. and Fink, S. (2003) Latent infections of Fomes fomentarius in the xylem of European beech (Fagus sylvatica). Mycological Progress. 2 (2). p141-148.

Edited December 28, 2015 by Kveldssanger

[sloth]

Thanks Jules for that link, I'll have a look when my laptop is online again.

Also this last fact, very interesting too nice1