From: d.lonsdale2@xxxxxxxxxxx.com
To: uktc@xxxxxx.tree-care.info
Subject: RE: Ganoderma applanatum/australe on n.maple - implications
Date: Wed, 21 Dec 2011 18:29:51 +0000
Dear Gerrit,
In answer to your question, I define the relevant terms as follows:
1. Biotrophic parasite: a parasite which obtains its nutrients from the
living cells of the host (usually by the penetration of those cells,
without killing them). Examples include rusts and mildews.
2. Necrotrophic parasite: a parasite which obtains its nutrients by
killing cells of the host (usually by the secretion of enzymes and/or
toxins). These parasites are usually able to grow also as saprotrophs (4,
below) and they are therefore often alternatively called "facultative
parasites". Examples include many fungi and bacteria that cause general
dieback and/or decay of host tissue.
3. Hemibiotrophic parasite: a parasite which obtains its nutrients both
as a biotroph (usually when it first penetrates host tissue) and as a
nectroph (usually at a later stage, after an initial biotrophic phase).
Examples include many organisms that cause leaf spot diseases.
4. Saprotroph: an organism which obtains its nutrients from the dead
remains of one or more living organisms.
As far as I know, there are no wood decay fungi in categories (1) or (3)
above. Some of them have the ability to grow into previously living
sapwood, causing it to die (or become "dysfunctional" and then causing
decay. I think that they can be regarded as necrotrophic parasites (2),
but I do not like to use this term without qualification, since many of
them live predominantly on wood that is already dead. This could be
sapwood that has been damaged by injury, or it could be central wood or
the tree, which has become heartwood or ripewood because of aging.
Traditionally, wood decay fungi have been described as "parasitic" if
they are found on living stems, branches or roots. I do not think that
this is correct if the fungus concerned is colonising only wood that is
already dead.
According to the above definitions, Ganoderma applanatum has been
observed to be mostly saprotrophic, whereas G. adpsersum/australe has
some capacity to act as a necrotrophic parasite. These observation seem
to be confirmed by some experimental work by my friends Schwarze & Ferner
at the University of Freiburg i. Br., Germany. (see:
http://www.enspec.com/articles/ENSPEC%20Research%20Paper%20-%20Ganoderma%20on%20Trees.pdf
)
Schwarze & Ferner found that G. adpsersum/australe was able to penetrate
defensive barriers (reaction zones), thus growing into functional
sapwood. It does not necessarily harm the tree seriously. Instead, it
might be able to co-exist with the tree for many years, instead of dying
out when it has utilised all the wood that was initially available to it.
In some cases, however, the fungus does enough damage to the sapwood
(especially in the roots of the tree) to cause the decline and perhaps
death of the tree. Also, the decay can, in my experience, become
overwhelmingly rapid if the wood becomes more aerated because of
excessive pruning or the storm-breakage of major branches.
As suggested in the recent correspondence, G. adpsersum/australe appears
to behave differently in different host species. I think that it can be
especially aggressive in species with which it has not co-evolved. I have
seen examples where G. adspsersum/australe (or perhaps a similar-looking
species of Ganoderma) seems to have killed exotic conifers such as
Araucaria araucana. I agree that it can cause extensive decay in the
broadleaved trees in your list. However, in Fagus sylvatica (one of its
main hosts in the UK), the tree and the fungus often seem to co-exist for
many years. The co-existence is probably even longer in species like
Quercus robur and Q. petraea, which have durable heartwood and therefore
tend to become decayed more slowly.
Regards,
David
-----Original Message-----
From: Viper Snake [mailto:snake24@xxxxx.nl]
Sent: 21 December 2011 14:14
To: UK Tree Care
Subject: RE: Ganoderma applanatum/australe on n.maple - implications
David,
1). Tony Croft has been using the term 'biotrophic parasite' in relation
to G. adspersum/australe on here. I questioned him about these labels and
asked him whether he could point me to any research that demonstrated
that the fungus was 'biotrophic' and/or 'parasitic', because this was
news to me, but he hasn't replied yet. Can you point me in the right
direction?
1). Tony uses my terms and the results of my in situ research on
biotrophic and/or necrotrophic parasites, which I already have explained
on Arbtalk, see : 2. http://arbtalk.co.uk/forum/529703-post53.html .
2). Similarly, that G. adspersum/australe is deterministically fatal to
Acers, no matter the circumstances, is also news to me. Where does the
research for this conclusion come from ?
2). From my own field research on the effects on the stability and
condition of different deciduous tree species of the biotrophic parasitic
G. australe, of which the mycelium causes a white rot with selective
delignification, that is most detrimental to Acer, Platanus, Populus,
Salix, Tilia, Aesculus (Anne Frank tree) and Quercus rubra.
Gerrit
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