Id Request: Small white asco on leaf petioles of ash perhaps

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Aciauda
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Id Request: Small white asco on leaf petioles of ash perhaps

Post by Aciauda » Sun Aug 05, 2018 2:46 pm

This fungus we found in abundance in leaf litter under ash, beech and oak with the odd Scots pine nearby. In one part of the wood it seemed to be everywhere we trod. The fruitbodies were up to 6 mm in diameter, on stalks that were black at the very base where they were attached to the black covering of the leaf petioles.
1 General view.jpg
General view
2 Close up 1.jpg
Close up 1
2 Close up 2.jpg
Close up 2
The excipulum was made up of textura prismatica near the edges of the fruitbody
4 excipulum 1.jpg
Excipulum near edge
And it became a palisade nearer to the stem
5 excipulum 2.jpg
Excipulum near stem

The trama deep to the surface lay in the same orientation as the surface palisade.
6 trama t. intrica.jpg
Trama of frutbody
The asci were 40x2.5 μm Melzer positive, paraphyses threadlike and featureless. Spores hyaline, somewhat clavate, smooth and 17.5 to 18.5 x 3.5 to 4 μm.


I have tried to key this one out in E&E, Nordic Macromycetes Vol 1 and in Peter Thompsons book, to no avail. To me it just does not seem to fit anywhere.

Paul Cannon
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Re: Id Request: Small white asco on leaf petioles of ash perhaps

Post by Paul Cannon » Sun Aug 05, 2018 4:15 pm

If the asci have croziers at the base (and the petioles do come from ash which seems likely to me) you have the notorious Hymenoscyphus fraxineus, causal agent of ash dieback disease. If there are no croziers, it will be H. albidus, a native non-pathogen occupying the same niche and in serious need of conservation. I hope it is the latter...

Best wishes
Paul

mollisia
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Re: Id Request: Small white asco on leaf petioles of ash perhaps

Post by mollisia » Mon Aug 06, 2018 6:29 am

Hello,

the fruiting periode of Hymenoscyphus albidus is decidedly earlier, May to June, whereas the pathogenic H. fraxineus fruits July to August.

So I would be very astonished if this would not turn out to be H. fraxineus.

In Germany I have not seen H. albidus anymore since at least five years.

best regards,
Andreas

Aciauda
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Re: Id Request: Small white asco on leaf petioles of ash perhaps

Post by Aciauda » Mon Aug 06, 2018 4:20 pm

Many thanks Paul and Andreas. I have searched and searched but found nothing but normal septa at the bases of the asci. Should I be looking for croziers at the bases of young asci or mature asci or anywhere else, please?

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Lancashire Lad
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Re: Id Request: Small white asco on leaf petioles of ash perhaps

Post by Lancashire Lad » Mon Aug 06, 2018 6:34 pm

Hi Archie,

In case it's of interest, there's good information, along with photos & drawings of H.fraxineus asci croziers in this paper: -
"Hymenoscyphus fraxineus vs. Hymenoscyphus albidus – A comparative light microscopic study on the causal agent of European ash dieback and related foliicolous, stroma-forming species". (Hans-Otto Baral & Martin Bemmann, Mycology, 2014, Vol. 5, No. 4, Pages 228–290).

The full paper is available online, and can be freely downloaded as a PDF via this link: -
https://pdfs.semanticscholar.org/11ad/8 ... 1533575989

Regards,
Mike.
Common sense is not so common.

Aciauda
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Re: Id Request: Small white asco on leaf petioles of ash perhaps

Post by Aciauda » Tue Aug 07, 2018 2:46 pm

Hi Mike
I am writing this to you and all others who are in Fungus UK community.

Many thanks for giving us all this remarkable paper. I have read the first part carefully, the part dealing with the two Hymenoscyphus species we are discussing. And I have looked for croziers in our specimens.

First I have gone back to the dried material. There I find the fruitbodies have that black/dark brown collar at their bases but the bases are not constricted, favouring Hymenoscyphus albidus.
Base of fruitbody not constricted.jpg
Fruitbody base not constricted


The bases of the asci have simple septa, I think. I have examined many of them in a prolonged session during which I took pictures of the ones which lay flat enough to photograph. These pictures are attached below. Is this evidence enough to assert that croziers are not there in our collection?
Asci basal septum simple (1).JPG
Basal septum simple 1
Asci basal septum simple (2).JPG
Basal septum simple 2
Asci basal septum simple (2).JPG
Basal septum simple 2
Asci basal septum simple (4).JPG
Basal septum simple 4
Asci basal septum simple (5).JPG
Basal septum simple 5
Asci basal septum simple (6).JPG
Basal septum simple 6
Asci basal septum simple (8).JPG
Basal septum simple 8

The problem remaining for me is the size of the asci. Ours are not more than 80 μm (and many are shorter)x4μm. 80μm is at the lower end of the ascus size in H.albidus and just at the lower end of permissable sizes for H. fraxinus stated to be. However in both species the ascus width is 10 μm as described in the paper.

Is it ok to claim that our specimens are H.albidus I wonder?

Yours

Archie
Attachments
Asci basal septum simple (3).JPG
Basal septum simple 3
Asci basal septum simple (7).JPG
Basal septum simple 7

mollisia
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Re: Id Request: Small white asco on leaf petioles of ash perhaps

Post by mollisia » Thu Aug 30, 2018 5:51 am

Hello,

I think the difference in the ascus size is due to the shrinking effect of dead asci. Did you compare the ascus measurements of your dead asci with the data given for living asci? Asci and often also spores in inoperculate ascomycetes shrink considerably when drying, up to 30%. Meaning an ascus which is 100 µm length when treating living material will be only 70-80 µm when you re-examine the same collection from exsiccated material.

best regards,
Andreas

Aciauda
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Re: Id Request: Small white asco on leaf petioles of ash perhaps

Post by Aciauda » Fri Sep 07, 2018 8:27 pm

Thank you Andreas, I did originally measure dry material but last week was able to go to the same woodland. In the same place we found fresh material. The asci in it measured the same as those in the paper this time. I searched diligently again for crozier clamps and again found nothing like any kind of clamp.
So the id is firm as I can make it - Hymenoscyphus albidus.

Thank you and everyone who has taken part in this to help me

Archie

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