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Hi! Tiny, black, oblong stromata with pure white

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Helotiales on "Polytrichastrum"?
Georges Greiff, 20-07-2019 22:51
Hello,

What appears to be a bryophilous member of the Helotiales has been found on the moss Polytrichastrum alpinum in Scotland.

Apothecia pale orange, approaching 1mm diam, appearing to lack a distinct stipe and margin.

(description incomplete)

Asci octosporous, biseriate, 48.9 - 55.3 x 6.24 - 7.80; paraphyses as long as asci, appearing to contain oil bodies in the apical cell only.

Ascospores polymorphic, hyaline, aseptate, often curved, 8.1 - 8.8 x 1.7 - 2.1.



It appears to be similar to the above two species, however the host is phylogenetically distant from P. formosum as P. alpinum should not be in genus Polytrichastrum.

The closest I am getting for this is "Bryoscyphus" turbinatus s.l. but the spores are too small. Any suggestions would be helpful, as would any guidance for staining, etc. I have enough material for further investigation.

Thanks,

Georges R. L. Greiff
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Hans-Otto Baral, 21-07-2019 07:54
Hans-Otto Baral
Re : Helotiales on "Polytrichastrum"?
Hi Georges
of course this is not B. turbinatus, also the low oil content does not fit. But probably some more characters deviate. Important is to study the excipulum (hyaline? globose cells?) and margin (any hairs?). IKI-reaction of asci, croziers? 

Spore size doe snot seem to be correct. When I take the longest spore as 9 µm, I get 1.3 µm width.

B. turbinatus is not host-specific, it may occur on very different mosses. This could recently be demonstrated by DNA (unpubl.) which concurred between Polytrichastrum formosum and and Hypnum cupressiforme.

Zotto
Georges Greiff, 21-07-2019 11:59
Re : Helotiales on "Polytrichastrum"?
Thanks, Zotto,

I will check these properties soon.

You have made me aware that my measurements are wrong - additionally the graticule on the microscope I am using is not fine enough for accurately measuring fungal material so will be replaced.

I will update this in due course.

Best Wishes,

Georges
Georges Greiff, 22-07-2019 17:47
Re : Helotiales on "Polytrichastrum"?
It took a few attempts to get these images loaded up. Additional information to follow.
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Georges Greiff, 22-07-2019 17:58
Re : Helotiales on "Polytrichastrum"?
There seems to be a significant variance in ascus and ascospore dimensions.

Asci: 40.72 - 58.54 x 4.84 - 8.65. Croziers appear to be present.

Ascospores so far (more need to be measured): 8.91 - 12.47 x 1.02 - 2.04

Excipulum composed on elongate, pigmented cells. Lacks hairs and true margin. Lower part darker.
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Hans-Otto Baral, 22-07-2019 22:55
Hans-Otto Baral
Re : Helotiales on "Polytrichastrum"?
Yes, this scpore length is more reasonable. But I think 1-2 µm is a too wide range.
And your asci are now dead, and the measurements include both turgescent and dead asci.

The excipulum looks interesting. But I have no idea for a genus. Did you test asci with IKI?
Georges Greiff, 22-07-2019 23:25
Re : Helotiales on "Polytrichastrum"?
Hi Zotto,

Apologies. The 2 micron measurement was an outlier as a result of a large bulge on one spore. I had written the dimensions in standard form with maxima / minima in parenthesis but this information all vanished when I tried to submit the text.

I am still getting to grips with ascomycetes and with finer resolution microscopy as you can probably tell. I think I will send the material forward to somebody with the appropriate equipment and reagents to make a proper analysis.

Thanks,

Georges
Georges Greiff, 26-07-2019 10:35
Re : Helotiales on "Polytrichastrum"?
Hi Zotto,

Just an update to say this might be Pezizella polytrichi Dennis 1962. The diagram shows a similar excipulum and the spore / ascus shape also fits.

Best Wishes,

Georges