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Transcript

SHARP EYESPOT! · Cereal Killers

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  Music.
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  Hi, welcome back to Serial Killers, the podcast all about the best diseases
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  and weeds of arable crops.
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  And today I was deciding which topic I should cover and research and one of
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  the diseases caught my eye as Dr.
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  Sharp and that was Sharp Eye Spot.
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  Puns intended. So Sharp Eye Spot is
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  a fungal disease of all cereals and it
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  is unrelated to another disease called eye
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  spots this is sharp eye spots the good
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  news is sharp eye spot is not as severe a disease
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  as eye spots so they're two fungal diseases
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  but this they're both unrelated and they
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  both got the same similar names because
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  they both have similar symptoms and that's
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  this eye spotting that can occur but hopefully
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  i'll tell you tell you the difference between the two different symptoms
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  so you can differentiate them because it's very important sharp eye
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  spot is nowhere near as bad as normal
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  eye spots but it is can cause you know some yield loss so it affects all cereals
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  as i said it's also reported to infect sugar beet cotton potatoes and turf grass
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  so however whether that is truly this species or a related species.
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  Not sure so it's many of
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  you will be familiar with the term rhizoctonia these are this is a genus of
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  fungal pathogens and very common there's lots of them there's you know there's
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  the most common one or most famous one is rhizoctonia solani which obviously
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  affects tomatoes and many other crops this one is rhizoctonia.
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  Cerealis cerealis? cerealis, yeah so obviously affecting cereals and those are
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  the crops that I mentioned it's obviously a lot of fungi have two scientific
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  names and so it's true scientific name,
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  has another scientific name which I'm not going to mention just remember it's
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  a rhizoctonia species, rhizoctonia cerealis that's all you need to know only
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  absolute and microbiology geeks need to know the two scientific names for this fungal pathogen.
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  So as I said, yield loss is not as bad as ISPOT or many other fungal diseases.
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  It's a disease that probably you may not even bother to control because the
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  yield losses are like half a percent and in extreme cases up to 25%.
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  But not in the UK, not so much.
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  Far more common to be on the lower scale i think in
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  asia it starts to become a real problem and
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  so it's thought that it occurs everywhere
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  around the world apart from obviously antarctica where you don't grow crops
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  but i've read wrong report that it doesn't grow it doesn't it doesn't affect
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  crops in south america but then i read another report that said that it's a
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  problem now in chile so there's no escaping the sharp eye spot Thank you.
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  It interacts with take-all, so you can get what I call potentiating or synergistic
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  effects, where you get increased or ramped up yield loss if those two things
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  are occurring at the same time.
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  So the reason it's called sharp eye spots is because you get sharply defined lesions,
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  as opposed to normal eye spot, where it's sort of like the dark lesions are the eye spotting,
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  so they're shaped like eyes is is much
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  more blending in so i
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  think it looks like what you get on like clematis where
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  a scale bug has been pulled off it
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  looks like something some sort of scab has been removed from the
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  plant but it's not that's just the lesion that it causes it's
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  got a clear dark margin around the epidermis and
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  that epidermis can be shredded and then unlike normal
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  eye spot it can be you know higher up
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  in the plant so 30 centimeters up whereas normal eye spot is is near the base
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  it so it's a fungal disease and it overwinters as strands of fungi what we call
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  mycelium on the stubble and on certainly on certain grass weeds as well and it can produce,
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  sclerotinia which are these large well for fungus anyway large bodies that sporulate
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  come the spring and so they can be a source of infection as well.
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  Certain forms of Rhizactonia can also live as saprotrophs.
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  These are fungi that live off decaying matter in the soil and then infect the plants.
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  So Rhizactonia solanii can live off as saprotrophic fungi, just not interacting
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  with plants at all, and then become a pathogen later on.
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  Now whether Rhizactonia soraleus does this, I'm not so sure.
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  Whether sharp eye spot can do this, I'm not sure.
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  It's certainly a necrotrophic disease when it is infecting plants.
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  And by this, I mean it gets into a cell, it kills the cell, and it consumes
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  the contents of that cell.
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  Hence the blackness of the actual eye spot and the tissues when it gets bad.
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  That's as opposed to, say, a biotrophic pathogen, which is basically acting
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  as a parasite on the plants, something like mildew or rust are an example of biotrophic ones.
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  It's thought that the disease is worsened or becomes more apparent when there's
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  cool autumns and spring around 9 degrees Celsius and you can get,
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  you know, that's getting worse diseases. But rhizoctonia is one of.
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  The plant can outgrow it, especially at lower temperatures.
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  So the lower the temperature, the more it can sort of, unless the rhizotone
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  is at the right temperature for it, it's one of these diseases where it thrives
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  when the weather condition is right, but the plant can sort of outcompete.
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  So the plant can't necessarily ward it off completely, it just outgrows it.
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  So severe infestation can cause
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  white heading of the of the actual produce and
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  it can cause lodging and both sharp eye
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  spots and the unrelated eye spot both cause
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  lodging because you're damaging the stem tissue okay so
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  this is acting on stems rather than than leaves it
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  likes acidic dry and sandy soils that makes
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  a change that you know fungus does it fungal disease
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  likes sandy soils normally it's like clay
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  soils where it's it's they prefer the
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  sort of damp conditions so liming addition will
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  help with controlling rhizoctonia because you're
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  going to increase the soil ph away from the optimum acidic conditions
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  and then you know foliar sprays of potassium silicate
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  will also make the cell wall stronger to resist the necrotrophic.
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  Fungus as it tries to get in and also it'll raise the ph of
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  the leaf tissue again helping with control now another
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  reason i'm interested in sharp eye spot is because
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  it's thought that one of the key factors
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  in effect whether it gets a successful infection is
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  the ability of the plant to produce chitinases and
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  recognize the disease before it gets in you get
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  these things called pamps and mamps which are pattern recognition molecules
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  that the plant detects and normally these are very important in biotrophic fungi
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  because they the the fungus tricks the plants into not detecting the chitin
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  on its cell surface but this is thought to also occur in rhizoctonia.
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  Serralis a sharp eye spot and obviously
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  that's an interest to me because at eutrema we make chitazan which
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  is basically a way of telling the plant that
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  there's chitin around and if you've got
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  diseases that are trying to turn off chitin receptors we just
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  go on and flood the plant with chitin and chitazan and
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  that overcomes that sort of that strategy
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  of the fungus so that's important what should
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  we say about sharp eye spots they also secrete
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  proteins to help with infection and metalloproteases
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  so metal linked protein degrading enzymes they.
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  Secrete polysaccharides and this all these
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  all suppress the plant's own ability to withstand
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  the infection
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  what's interesting about those metalloproteases there's
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  metal linked protein destroying enzymes is that
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  they're linked to zinc and i find this interesting because
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  normally zinc is
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  like an anti-fungus metal you
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  know you think of zinc containing fungicides zinc is
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  highly toxic to fungus but actually sharp
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  eye spot needs zinc in small amounts to actually
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  have its activity to produce these metalloproteases
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  to trick the plants into thinking it's not there so that's a really interesting
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  one so zinc is actually important for this this fungus obviously don't go without
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  zinc for your crop i'd never revised that so it's not like a control strategy
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  getting rid of zinc it's just a quirk an interesting feature there's been a
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  lot of study in china on sharp eye spots because.
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  It's it wasn't there until or it
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  wasn't a problem until maybe like 2005 to 2015 in
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  which case it really ramped up its problem
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  and one of the i've tried to do some research on like susceptible species and
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  the only one that i could find was when my six which is clearly a chinese name
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  for a variety whether that's got an english name i don't know and it's thought
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  to be important you know effected tillering in in this when my six.
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  And so we say it could potentially be a saprotroph in the soil.
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  So it could be another disadvantage of no-till.
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  Other interesting facts about sharp eye spot, it's a basidiomycete.
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  And that's a type of fungus. If you're a microbiologist or you've done any microbiology,
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  you'll know what a basidiomycete is.
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  And then eye spot is an ascomycete. So that's very different.
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  That's like saying the difference between a grass and a conifer or an orchid.
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  They're completely different genetically. they're just
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  you know symptoms are the same they have two nuclei
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  per cell so humans plants
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  they have one nucleus per cell
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  but this fungus has two or and the
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  rhizoctonia can have up to five nuclei per
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  cell that makes genetic study of the
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  disease fairly difficult there's a number of complications that
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  come with that as i said it affects the vascular system and
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  the sheath of the of the of the grass and so
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  that's where the lodging comes in and it
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  affects nine million hectares in china as of
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  2015 probably more and then obviously went to chile
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  in 2015 as well there are no resistant varieties
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  according to the chinese reports i read however perfectly acceptable for people
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  to comment and say there is resistant there are resistant varieties and And
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  one of the interesting research areas the Chinese researchers were looking at
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  was RNA-based products.
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  RNA is a similar compound to DNA. It's nucleic acid.
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  And there's this RNAi technology where you can interfere with the expression
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  of genes in a pathogen or a plant or a human.
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  And this RNAi technology could potentially be used to sort of knock out the
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  pathogenicity genes in the fungus.
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  So, you know, you've got... But for this to be sort of licensed and to be commercialized
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  in the UK, it would have to be a very, very serious disease.
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  So Sharp Eye Spot is not going to be the first RNAi disease to get a product...
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  For it it's probably going to be something like you know black grass or fusarium something far more.
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  Problematic for the for cereal ground so as
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  i say that's that's sharp eye spot i thought i'd cover that
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  normal eye spot we might maybe i'll cover that next far
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  higher yield loss the lesions are lower
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  down they're darker and they're not confined to
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  the outer sheath of the plant it penetrates through the
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  stem and obviously that's going to make it far more
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  worse from it from it from that perspective so that's
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  serial killers for today i thought i'd start
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  doing more podcasts because it's coming into the spring and
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  to be truthfully honest i'd like some more customers arable customers coming
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  into spring buying loads of our products like phosphorus liberator and liquid
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  gypsum and all the cool things that we produce i've just produced a biologicals
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  program naturally and it goes through and it lists all the different biological
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  products you can put on a crop,
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  throughout the growing season so if you'd like to receive a copy of that biological.
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  Biological program for cereals let me know and i
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  will send one an email i'll post one to you i started
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  just slapping them on farm gates as well this
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  is my new strategy i used to give out brochures to
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  farms and i'd always struggle to find the
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  post box for the farm because you you might have the shed with the.
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  Sprayer in but does the farmer live near there who knows you
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  know the farmhouse might be you know often it's not
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  the farmer that lives there so i've got this new strategy and i've
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  got these these uh plastic sheets here that you
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  need the documents enclosed sheets you have to get on parcels or
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  pallets and i just find find where
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  then the farmyard is and just slap that on a gate and i
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  found it's remarkably fast how someone appears from
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  around a corner as soon as you put one of those on
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  someone's gate because i think they think it's like a summons a
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  court summons or something like that or a you know an eviction
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  notice or something like that and everyone's like excuse me
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  what are you doing and i'm like oh hello i'm just
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  a biological crops input person and so
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  yeah that's my new strategy and i don't know how people find me as
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  soon as i slap one of those on but people do come out
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  of the woodwork as soon as i've started doing that if it's if it's
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  too annoying i'll stop but for now it's it
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  also stops me from going into uh as an introvert i don't like going
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  into a farm farm farm houses and
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  going up to the doors especially there's lots of dogs that suddenly appear and
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  but yeah my my sons find that hilarious because sometimes
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  i take i take them to farms as we're traveling past them and say we're looking
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  out for cereal farms not animal farms and then we we turn up and then they see
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  me being attacked by about three or four dogs and yeah that's hilarious to them
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  but yeah so if you were if you're interested in applying for products that would
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  control fungal diseases like cereal icebox.
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  We've got things like arcytosin, or silicates, or salicylic acid,
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  all sorts of wonderful products.
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  Speak to you, Tremor. Thank you very much.