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Hymenoscyphus sp. on twigs, leaves and petioles

Ethan Crenson, 09-10-2024 05:05

Hello all,

I found this tiny pale yellow Hymenoscyphus on twigs, leaf petioles and leaves of what may have been fraxinus in a wetland area in New York City in the Bronx. The forest was composed of ash, maple, oak and sweet gum.

The apothecia are about 1.5mm tall with a yellow hymenium. The stipe is lighter in younger specmens, but becomes brown in older specimens.

Spores are hyaline, multi-guttulate usually with 2-4 larger guttules and several smaller ones, some curved, many with one blunt end and one acute end. Dimensions:

14.2-21.6 x 3.6-6.0µm
Me: 18.6 x 4.8µm
Q: 2.4-5.3
Qe: 4.0
N=15
Asci, clavate, IKI+, with croziers. Dimensions:
91-112 x 8-12µm

Paraphyses with tiny guttules, cylindrical, about 3µm wide.

Ectal excipulum textura porrecta. Some brown pigmentation in the Ectal.

It is not certain that the substrate is Fraxineus. As far as I know Ash dieback caused by H. fraxineus is not reported from North America. (Unfortunately, I get a overwhelmed with Google results leading me in that direction if I include the possible substrate in my searches).

Any help would be appreciated.

Thanks!
Ethan

Hans-Otto Baral, 09-10-2024 10:21

Re : Hymenoscyphus sp. on twigs, leaves and petioles

I actuallly think it could be Hymenoscyphus fraxineus. maybe you could try to make a section of the stipe base (which is not as dark as in H. fraxineus) for the included crystals which I consider characteristic of this and H. albidus.

Michel Hairaud, 09-10-2024 15:28

Re : Hymenoscyphus sp. on twigs, leaves and petioles

Hi Ethan and Zotto,

Looking at the spores, I wonder whether there are very short (1-2 µm long maxi) cilia at their ends or not ?

Amitiés Michel

Ethan Crenson, 09-10-2024 15:56

Re : Hymenoscyphus sp. on twigs, leaves and petioles

Zotto and Michel, thank you for your comments. Zotto, maybe have I misinterpreted the presence of croziers in the 11th photo? I am not certain, but I thought that H. albidus had no croziers. I don't have much experience with Hymenoscyphus. Michel, my photos are not too clear unfortunately. (My usual microscope is out for repair). I guess the cilia might be easier to detect in KOH, assuming they would not dissolve or otherwise disappear. I'm running low on apothecia so I want to ask before I waste resources.

Ethan

Michel Hairaud, 09-10-2024 16:14

Re : Hymenoscyphus sp. on twigs, leaves and petioles

H. albidus spores have no croziers , you are right, Ethan and it makes a difference with H. fraxineus , also on Fraxinus petioles. I think your pics do show croziers.

I am not sure KOH would help with the observation of cilia . I join your plate with the suspected spore ends with short ones, but not sure. I also join a picture with H. scutula spores with short cilia to compare. But H. scutula has no croziers and it grows on plant stems rather than twigs.

Michel

Hans-Otto Baral, 09-10-2024 17:04

Re : Hymenoscyphus sp. on twigs, leaves and petioles

I fully agree with Michel. I only meant that these crystals in the stipe base occur in both species. The croziers are very clear nd I think the small protuberances at the spore base may occur in H. fraxineus/albidus too.

Martin Bemmann, 09-10-2024 17:36

Re : Hymenoscyphus sp. on twigs, leaves and petioles

But it would be alarming to see H. fraxineus in the US. As of 2022 it did not occur there https://download.ceris.purdue.edu/file/4332

Regards

Martin

Michel Hairaud, 09-10-2024 21:34

Re : Hymenoscyphus sp. on twigs, leaves and petioles

Thanks, Martin, I was about to ask whether H. fraxineus has already been detected in North America

Amitiés. Michel

Ethan Crenson, 10-10-2024 05:17

Re : Hymenoscyphus sp. on twigs, leaves and petioles

I was unable to see anything resembling cilia at the ends of the spores. There appears to be a tiny knob, or protuberance in some of the larger spores. I was unable to find crystals in the stipe.

I agree that it would be alarming to see H. fraxineus in North America. I feel this must be some other Hymenoscyphus. I may have misdirected the conversation by suggesting Fraxinus —it is still possible that the substrate is something else.

So that I can have a better understanding of how to approach the study of Hymenoscyphus, what are important features I should be looking for? Cilia at the spore ends? Crystals? What else comes into play?

Thank you all again for your help.

Hans-Otto Baral, 10-10-2024 09:33

Re : Hymenoscyphus sp. on twigs, leaves and petioles

What is not clear on your pics is the content of the living paraphyses. H. caudatus is excluded as it has simple-septa at the ascus base. It has also often VBs with a low refraction, wheres H. fraxineus/albidus has strongly refractive VBs. The main feature remains the living spore and its contents

Martin Bemmann, 10-10-2024 10:40

Re : Hymenoscyphus sp. on twigs, leaves and petioles

Hi Ethan,

it would nevertheless nice to check the (possible) host.

There is e.g. a lot of Fraxinus americana in the Bronx River Park (see attachment).

https://tree-map.nycgovparks.org/tree-map/species/36480

Regards

Martin

Viktorie Halasu, 10-10-2024 11:24

Re : Hymenoscyphus sp. on twigs, leaves and petioles

Dear Ethan,
can you please make a section of the petiole (or rachis), in water? Some other hosts with long petiole (eg. Acer, Q. rubra) can be excluded by its anatomy.
Viktorie

Ethan Crenson, 10-10-2024 22:46

Re : Hymenoscyphus sp. on twigs, leaves and petioles

Viktorie, Hopefully a cross-section under the dissecting scope at 30x will be sufficient. I can mount this in cotton blue or congo red and look under the compound scope, if necessary. But I am packing my gear to go to a foray for the weekend, so there may be a delay.

wood-6919-0001.jpg

Ethan Crenson, 11-10-2024 00:07

Re : Hymenoscyphus sp. on twigs, leaves and petioles

Zotto, I am also hoping to provide better images of the paraphyses. Here I will be honest, there are narrow and broad paraphyses... or am I mistaking immature, developing asci for paraphyses in the case of the broad structures. Sometimes I'm not sure.

I also had another look at the base of the stipe. The cells of the main part of the stipe seem to be textura porrecta, but at the very base the cells are textura globulosa. There again I don't believe I see any crystals, unless the brownish pigments I am seeing there are the crystals I'm looking for. (the image of the stipe base is uploaded as a file, the paraphyses are photos in directly in the forum)

Ethan