Friday, 8 May 2020

Kuehneola uredinis (or not?)


This orange-streaked bramble stem caught my eye today. 

Bramble Rubus fruticosus agg. hosts a few species of rust fungi but, as far as I know, only one which looks like this. These longditudinal pustules are the uredinia (stage II) of Kuehneola uredinis.

The UK species inventory lists its preferred common name as Pale Bramble Rust, with Bramble Stem Rust also in use. But they're both rather unsatisfactory. At this stage in this species' life cycle you can see it's very much not 'pale'. And at other stages of its life cycle you'll find it on growing on the bramble leaves, not the stem. So I'm inclined to forget the common name for this one.

I think you can get away with identifying this species from its field characters, but I did have a look at the uredospores.

I think this is what they're supposed to look like! I guess that's an immature one on the left, with a stalk still attached?

UPDATE 10/05/2020

OK - turns out this one isn't quite as easy as I thought. Apparently Phragmidium bulbosum can also look similar in the field and occur on bramble stems.

Differences between P. bulbosum and K. uredinis sound rather subtle to me (with reference to Dutch Rust Fungi). 
  • P. bulbosum should have paraphyses, but I can't figure out what they'd look like. 
Is that stalked thing in my image above a paraphysis? I'm inclined to think it's a spore; I saw reference in Wilson & Henderson's 'British Rust Fungi' to Phragmidium spores being "borne single on pedicels" - so perhaps the stalk-looking thing is a 'pedicel'?
  • P. bulbosum uredospores are 'distantly echinulate' whereas in K. uredinis they're 'densely and finely verrucose/echinulate.
This is the best illustration I can find of that distinction:

Reproduced from 'British Rust Fungi' by Wilson & Henderson (1966).
Incidentally, Grove (1913) seemed to have a completely different view on what K. uredinis spores look like.

Wilson & Henderson treat Grove's K. albida as synonymous with K. uredinis; but that uredospore illustration in Grove looks suspiciously like Wilson & Henderson's illustration for P. bulbosum. Hmm... Confusing!

The Plant Parasites of Europe website has images of K. uredinis uredospores (here) but no comparable photos for P. bulbosum.

I got this other micrograph of my collection, which shows something spotty, i.e. a 'verrucose' or 'echinulate' uredospore? I don't know why it's clear (hyaline) – did the fungus produce an empty spore for some reason? Maybe the other ones look like this too but you can't see the details of the uredospore wall usually, against the orange contents...?  

  • Also P. bulbosum is described as 'yellow' and K. uredinis is 'orange-yellow'. Well, I would describe my collection as 'orange-yellow' but that's not much to go on.

Anyway. I've read everything I can think of to read, and googled everything I can think of to google and I'm still not sure what I've got here. Might have to ask an expert.  

UPDATE 25/05/2020

OK - so I feel like I left this one kind of unfinished... And the help I received in the comments here and via the British Mycological Society Facebook page have spurred me on to have one more look at this bramble stem rust.

Brian Douglas let me know that the paraphyses of Phragmidium should look something like this. And I was advised to look at a cross-section through the stem rust pustule, to have a proper look for them. So that's what I did. Here is a shapshot from one of the cross-sections I looked at.

I'm now pretty sure my collection doesn't have paraphyses. So I'm going with an identification of Kuehneola uredinis.

I've learned a few other things along the way. The clear structure I was talking about earlier is a dead spore. You can see another one in the image above.

The growing spores are held on a stalk called a 'pedicel' - and that is what I was looking at in my first micrograph.

For the record
Identification: Kuehneola uredinis
Date: 8/5/20
Location: Home, West Sussex

Thursday, 7 May 2020

Withered grass

I think I mentioned the other day I've been reading 'Rust, Smut, Mildew & Mould' by M.C. Cooke (5th edition,1886). It's a terrifically engaging introduction to these microscopic fungi.

Whereas modern texts on 'plant disease' can be rather dry and scientific in style, 'Rust, Smut, Mildew & Mould' presents the study of these fungi as a thrilling voyage of discovery.
"We might traverse the primeval forests of the new world, and explore the unknown regions of the old, and not encounter so much to excite our admiration, or cause our wonder, as lies about our feet at home; marvels which we tread beneath our feet, or kick from our path, because they appear to be only rotten sticks, withered grass and decaying leaves. All this may appear as the dream of an enthusiast, or the ravings of one on whom the moon has shone too often. When Columbus spoke of a new world beyond the seas, which longed to seek and explore, some believed him duped, and others called him mad. We write of no chimerical El Dorado, we speak of no undiscovered world, and yet we seem to allude to wonders still unknown, because so few have had the courage to venture upon the journey for themselves."
Cooke's book ran to six editions and must have encouraged many readers to pursue detailed studies of these microscopic fungi – discovering important economic applications for this knowledge along the way. Nowadays, plant pathology is primarily the preserve of academic and agri-industry types. For the amateur it seems a relatively obscure branch of mycology, in the UK at least. Unless you happen to live in Wales, where there is a thriving 'rust study group' – responsible for producing a number of attractive publications which provide a modern stepping-in point to the study of rust, smut and mildew:
  • Rust Fungus Red Data List and Census Catalogue for Wales (here)
  • Smut and Allied Fungi of Wales (here)
  • Downy Mildews and White-blister Rusts of Wales (info here)
One (not-insurmountable) barrier to studying these fungi in any detail is the need for a microscope and knowledge of how to use it. In Cooke's day, amateur microscopy was quite the craze. He himself was a founding member of the Quekett Microscopical Club (which still exists today, I wanna join!) and would spend evenings at the microscope with fellow enthusiasts.

Microscopists (left, Cooke; right, Berkeley) examining the potato blight fungus. From a cartoon by W. G. Smith, Graphic, 1875. Reproduced from the biography of Mordecai Cubitt Cooke by Mary P. English.
Any long-time readers of this blog will know that the road to basic competence with a microscope has felt like a long one for me. As a 21st century amateur mycologist, opportunities for practical instruction are relatively few and far between. But when they do come along, it makes such a difference having someone actually show you what to do.

I now find myself in the fortunate position of having a good microscope and some knowledge of how to use it. So when my birthday came around, under 'lockdown', I thought I'd treat myself to a new eyepiece camera and a few other bits...

... and I headed out into the back garden, in search of "withered grass and decaying leaves".

I didn't have to go far. The Sweet Vernal-grass Anthoxanthum odoratum in our 'mini-meadow' was covered in rust.

The rust appeared to be 'epiphyllous' – growing only on the leaves...

... forming these scattered orange-brown spots. I fathomed that these must be the 'uredinia' of a Puccinia species; stage II in the rust fungus's life cycle.

You can see how the uredinia have burst through the leaf's surface. Look closely and they're made up of masses of uredospores.

Here are some of those uredospores at 400x magnification. Mounted in water so you can see their true colours.

I didn't know what these wiggly things were. But reading around a bit, I figured out they're paraphyses. The presence of paraphyses, and their shape, is significant when it comes to identifying these rusts.

There's a good, up-to-date, book on rust fungi, 'Dutch Rust Fungi', which the authors have made available online, here. This gives two species of Puccinia occurring on A. odoratum: P. graminis and P. brachypodii. The presence of thick-walled paraphyses, as seen here, suggests P. brachypodii s.l..

The description in 'Dutch Rust Fungi' states that "taxonomic interpretations of this species are manifold" and other authors recognise different species. Elsewhere, I found a description of P. poae-nemoralis on the Plant Parasites of Europe website (here), which seemed to match my observations well, with reference to "hyaline paraphyses that bear a distinct head and often are sharply bent just below".

I consulted with the experts on the UK Fungi forum and received a very informative response from Paul Cannon (here) – providing some additional insights into the complicated world of rust biology and taxonomy. He advised recording this observation under the name P. anthoxanthina (in the sense of Klenke & Scholler's 'Pflanzenparasitische Kleinpilze', 2015); although in the Checklist of British & Irish Basidiomycota this name is considered to be synonymous with P. brachypodii var. poae-nemoralis (so I was on the right track!) and P. brachypodii var. poae-nemoralis is preferred.

It is easy to get hung up on names and worry about selecting the 'right' one, or – horror! – giving your collection a wrong one. The way I see it, a name is just shorthand for a suite of characters observed. Names are useful, as a way of accessing information on people's understanding of nature. But the observation is the important bit: make a good record of your observations and let this be the truth of what you saw. A name is just for our own convenience: a folder in which to file ones observations.

But that's easy for me to say. I am a very slow mycologist; content to wonder at the marvels which we tread beneath our feet.

For the record
Date: 3/5/2020
Location: Home, West Sussex

Saturday, 25 April 2020

Violet rust is orange

There's a place near my back door where the violets grow. They've seeded themselves there and I am happy to encourage them in this shady strip where nothing much else grows.

Recently I've been reading an old book on 'Rust, Smut, Mildew & Mould' by Mordecai Cubitt Cooke (5th ed., 1886 — you can find it in the Biodiversity Heritage Library, here) and was particularly struck by a description of one species of rust ...
"... which attacks the violet. The sweetest of flowers as well as the earliest, in despite both of its odour and its humility, becomes a victim to one or more of the ubiquitous race of fungi. Thickened spots at first appear on the leaves; the petioles, or the flower stem, or even the calyx, become swollen and distorted; and at length the cluster-cup breaks through."
So I've been keeping an eye on the violets, wondering if I'd catch sight of these so-called 'cluster-cups'. This morning, I found what I was looking for.

Glancing down from above, it was hardly noticeable. But looking closely at each plant, I found the rust was present on lots of them: on the leaves, the petioles and even the calyx — just as Cooke had described.

Correctly identifying the host plant is a critical step in identifying rusts and often the trickiest part for me. I'm no botanist, but when I was a girl my mum used to 'keep things interesting' on a long walk with a promise of two pence for every plant I could name (twenty pence in winter) — so I can get as far as... "dog violet?"

Happily, Sussex Botanical Recording Society has shared a brief guide to Sussex violets, here. And I think the pale upturned 'spur', notched at the end, suggests Common Dog Violet Viola riviniana.

Scientific knowledge and taxonomy of rusts has moved on somewhat since 1886, so — armed with a hopefully-accurate ID on the plant — I consulted a more modern tome to identify the rust. I've just recently acquired a .pdf of 'Dutch Rust Fungi' (from here) and it includes helpful keys as well as descriptions and illustrations, in English as well as Dutch. I conclude that this 'cluster-cup' — the 'aecial' stage in the rust's life cycle, also known as stage I — is Puccinia violae.

Here is a close-up of those beautiful little 'cluster-cups' on the underside of a leaf. 

The book on 'British Rust Fungi' by Wilson & Henderson (1996) includes a more detailed description of the 'cluster-cups', or aecia [singular = aecium], of P. violae. The outer wall of the 'cup' which you can see here is known as the peridium and is described as having a "white torn revolute [meaning 'curled back'] margin", which you can see here in a focus-stacked image of my collection.

The orange mass inside, and the tiny orange specks scattered about on the leaf's surface, are the aeciospores. Poised to infect their next victim... — if you frame it in Cooke's terms. Or just being aeciospores... — if you're inclined to be less judgemental about this thing called life

I don't think there is a 'Spotters Guide to Rusts' but, if there was, this species would surely be in it as it's apparently a common one to find. Ingram & Robertson mention it in their book on 'Plant Disease' (1999) and it's an example of a rust fungus which lives out its whole rather elaborate life cycle in association with one species of plant, in this case Viola riviniana, so it's known as 'autoecious'. There are photos of the rust's other life stages on the Plant Parasites of Europe website, here. So naturally I'll be looking out for those! Although they're rather less showy.

(I've got another rust in the garden which spends part of its life on my Pendulous Sedge Carex pendula and part of its life on something else — possibly the nettle patch or my fruit bushes — but I'm still trying to get to the bottom of what's going on there, so will have to save my 'heteroecious' rust fungus for a future blog...)

For the record
Date: 25/04/2020
Location: My garden, West Sussex

Saturday, 18 April 2020

Lockdown foray

I'm taking part in a 'lockdown foray' today with other folks over on the British Mycological Society Facebook page, in memory of Richard Shotbolt.

Here's this morning's finds from my garden in West Sussex.

An aging patch of garden bluebells provided my first find...

... the distinctive, elliptically arranged pustules of Bluebell Rust Uromyces muscari.

Tucked away at the back of the garden, a self-seeded tutsan (Hypericum sp.) was showing telltale yellow spots on a few of its lower leaves.

Tutsan Rust Melampsora hypericorum seems a likely identity for this one. I recall I found something like this before at Rowland Wood, here.

I think I've got something similar on the Petty Spurge Euphorbia peplus that grows in the cracks on the patio: Melampsora euphorbiae. I've recorded this in the garden before, here.

Then the plant identification gets a bit challenging... The tiny white flowers on this plant have six stamens and I think it might be Wavy Bittercress Cardamine flexuosa.

Whatever it is, it's got some impressive white blisters on its leaves.

Looking in 'Microfungi on Land Plants' by Ellis & Ellis, I'm thinking this must be the 'white rust' Albugo candida. But it's not a fungus! It's an oomycete. So I lose a point there.

Next up I've got some fuzzy-looking spots on the underside of a cultivated primrose.

From the top, you can just make out some brown spots and the leaf is yellowing around them.

I'll be honest, I don't really have any idea what this is. Is this what downy mildews look like? Kinda fuzzy-looking?

I can see loads of what-I-assume-are fungal hyphae. But I don't think I'm anywhere close to an identification with this one.

I had a couple of things on some dead currant twigs.

There was this black, bristly looking thing. I thought it might be Chaetosphaerella phaeostroma, which I've come across before (description here). But all I'm seeing is black bristly stuff, and no fruit bodies which might help me confirm an identification. Hmm.

These tiny yellow specks looked like they must be something fungal. 

They are miniscule cup funguses!

Not sure how to progress towards an identification with these, as I think there are a few different genera that can look like of like this: e.g. Bisporella, Calycina and Orbilia?

Finally, I've got this poroid resupinate fungus which was growing on the underside of a plank that was lying on the ground.

Hmm. I've been flicking through 'Fungi of Temperate Europe' and there are rather a lot of species that look a bit like this. Might give up on this one!

For the record
Date: 18 April 2020
Location: My garden, West Sussex

Friday, 17 April 2020

Rust Quest

'Rust Quest' was a bit of nonsense I came up with last summer, to add a little excitement to my fungus forays. This was one of my more memorable finds – on the patio! – just shared on Twitter at the time.

Now seems like a good time to seek out a few more rusts and smuts around here!

For the record
Date: 9 July 2019
Location: Small Dole, West Sussex

Monday, 13 April 2020

Crystals in the leaf litter

Another day, another poke about in the garden.

This dead bramble leaf provided much distraction today. More specifically, it was the tiny grey blobs on the bramble leaf that caught my eye. See 'em?

Once I'd got them under the stereomicroscope, I could see that they were the 'fruit bodies' [sporangia] of a slime mould. So I got my slime mould book out: 'The Myxomycetes of Britain & Ireland' by Bruce Ing. I don't have much experience with slime moulds, but I guessed this one might be a Physarum species...

The sporangia were just stunning to look at under the microscope so I spent a while getting a focus-stacked image of one. I saw that the outer surface [peridium] is covered in frost-like particles.

Focus-stacked image of the peridium. Around 40x magnification.

The round mass of spores, enclosed by the peridium, sits on top of a stout white, slightly furrowed stalk – shown here on one of the sporangia which had neatly broken into cross-section.

Focus-stacked image of a sporangium in cross-section. Around 40x magnification.

You can see here the round flat base to the stalk which anchors the sporangium to the surface it's growing on: the hypothallus. From the tip of the stalk [the columella] tiny threads radiate outwards; these threads form the capillitium: the structure which holds, and assists dispersal of, the spores.

Here are a few of those threads under the microscope.

Section of capillitium. Mounted in water, 400x magnification.

Flicking through Ing's book, the description of Physarum leucopus sounded close to what I was looking at. But it noted also a "close resemblance to Didymium squamulosum".

I dipped into the British Mycological Society Facebook page, to see if previous discussions there would illuminate the difference between these two species... And I found that Steven Murray had commented on a similar-looking collection last year (here) that angular star-shaped crystals are indicative of Didymium.

I scanned across the material I'd prepared under the microscope. And I think I've found what I was looking for.

Star-shaped [stellate] crystal shown with two minutely-warted spores. Mounted in water, 1000x magnification. Focus-stacked image.

Wow! Slime moulds really blow my mind. How do they create crystals out of bits of old bramble? Damned if I know.

I think that makes my collection Didymium squamulosum.

For the record
Date: 13 April 2020
Location: My garden, West Sussex

Saturday, 11 April 2020

The Joy of Sticks

One unexpected consequence of our current circumstances is that my garden – the location for Michael Blencowe's daily 'Corona Wildlife Diary' – has become ever so slightly famous.

It's been a joy to see people sharing stories of life, wild life, continuing on around us. But when the camera turned to my back garden, I confess to a sudden and powerful empathy with Hyacinth Bucket and that matter of 'Keeping Up Appearances'. Because – with time taken up by work and other interests – our garden had become a bit of a mess.

So it was that I found myself on the first day of the bank holiday intent on tidying up the 'vegetable patch'.

Last year's Fennel has stood here all winter; its stems now well and truly dead. So I thought I'd start by clearing these away. It took longer than I thought as, while I was chopping them into bits to go in the garden waste bin, I got rather distracted by the tiny bumps and speckles which adorned them.

The thin stems in the Fennel's upper reaches were most intriguing, being covered in a smattering of tiny fuzzy-looking specks. So some of these were saved from the garden waste bin and came into the house with me. I popped them in a box with some damp kitchen roll and waited to see what would happen.

Here's one of those stems after it's moistened up a bit. You might just be able to make out those fascinating specks?

Another hour or two passed, while I figured out how to change a light bulb in the stereomicroscope.

It was worth it, because these aren't just any old specks. They are in fact beautiful soft grey cup funguses fringed with crystal-white hairs.

At the highest level of magnification, I could just make out some tiny square clusters of dots – a telltale sign that what I'm looking at here is a fungus which holds its spores out on prongs [sterigmata]: it's a basidiomycete.

I think what I've got here might be Lachnella alboviolascens; but there may be similar species and I haven't yet managed to track down a key.

The authors of 'Fungi of Temperate Europe' describe Lachnella as "a genus of dessication-tolerant cyphelloids... In dry weather the fruit bodies close and form small, hairy balls." You can actually see this in action under the microscope – these photos were taken over the course of about 15 minutes.

Those weren't the only interesting specks on the Fennel.

The thick stems were covered in tiny black bumps which – taking a lead from 'Ellis & Ellis' – I think might be Leptosphaeria libanotis, with a "depressed-globose" shape.

I can't work out if the even-tinier specks shown here [TOP] with the Lachnella for scale [BOTTOM] is a baby version of the Lachnella, or something different. Might need to get the slide microscope out...

Anyway, I think we've established why the garden's such a mess. And maybe messy's just fine for funguses.

For the record
Date: 11 April 2020
Location: My garden

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