Last Chance Saloon

[Tim Harberd]

Hi Folks,
   I have four little clumps of Augustus… The two best clumps are showing stripey leaves. I have now learned that Augustus is well know for carrying virus. This raises a number of questions for me:

1) Is it time to compost all my Augustus?
2) Since all four came from the same source, is it possible that any of my Augustus are clean?

   I know that, it some plants, tissue culture has been used to ‘clean’ stocks of virus. The much discussed twin-scaling is a form of tissue culture. So:

3) If I excised twin scale bulbils as soon as they formed, and plated them on agar, might I get virus free stock
4) Would it be possible to raise virus free stock by plating thin slithers of the basal plate directly on to agar?

   I’m thinking it would be quite easy to make the agar using boiled Augustus bulbs!!

Tim DH

[Alan_b]

I presume tissue culture works because you may be lucky enough to culture a piece that is small enough to be uninfected.  So your plan might just work.  But people seem content to grow all sorts of virused bulbs, tulips spring to mind, if the virus produces a petty effect and does not weaken the plant too much.   

[mark smyth]

clean Augustus are now available.

I dont actually worry too much about virused snowdrops. I'll be spraying soon for aphids

[johnw]

clean Augustus are now available.

I dont actually worry too much about virused snowdrops. I'll be spraying soon for aphids

Mark - I thought last year it was decided the clean Augustus was in fact infected despite the cost!

In any event the infection certainly doesn't slow the old Augustus down, I wonder just how infectious it is.

johnw

[kGarden]

   I know that, it some plants, tissue culture has been used to ‘clean’ stocks of virus. The much discussed twin-scaling is a form of tissue culture. So:

3) If I excised twin scale bulbils as soon as they formed, and plated them on agar, might I get virus free stock
4) Would it be possible to raise virus free stock by plating thin slithers of the basal plate directly on to agar?

When I was young I worked on a nursery that used tissue culture to remove virus from plants, mostly cut flowers.

They kept a greenhouse at absurd temperatures, I guess it was 40C or so, on the theory that at that temperature virus replication would shut down, so any cell division that the meristem made would not be re-infected, and then taking the meristem tip under a microscope for micro propagation would yield a virus free product.

In practice it was pretty hard to persuade the plant to do any cell division at that temperature either!

Not sure how/if that could be applied to bulbs and twin-scaling equivalents though?

[steve owen]

Tim
People get quite exercised about virused Augustus, and "clean" stock is available. But the virus doesn't seem to infect other varieties. You might want to plant it in lattice baskets slightly away from other galanthus, but I would say keep growing and enjoying it.
Steve

[RolloP]

This post is to answer a few of the questions posed byTimDH at the start of this thread.
 "Augustus " has a Poty virus (Potato Y complex) which has been identified as  "Narcissus Late Season Yellows Virus". Other Snowdrop varieties that have this particular virus are "Melanie Broughton"( leaf mottles when under stress) and "S Arnott"( no visual symptoms & also has Cucumber Mosaic Virus )  It would seem that this virus does not occur in many varieties and does not easily spread.
 " Clare Blakeway Phillips" has "Ornithogalum Mosaic Virus". This virus has not been found in any other variety, indicating that it also does not easily spread.
  The most common virus group found in Snowdrops is "Cucumber Mosaic Virus".
  CMV has been found in "Peter Gatehouse", "Godfrey Owen", "Comet", "Janquenetta",
"Trym","Trymlet" and "South Hayes".  In the case of the last three varieties, it would seem that this strain of CMV is seed transmitted.  Not all strains of CMV are.
 CMV seems to cause smudging of pigment on the inner petals ( PG),  pigmented spots on the tips of  outer petals ( Comet & Janquenetta) and pigmented blotches on the outer petals (Trym and similar).
 So what  do we have with regards to virus in Snowdrops ?
 One group which causes leaf and flower symptoms , which is not easily spread to other plants, and another which does seem to spread more easily but which causes flower markings which many people admire and want to grow.
  The sort answer to virus in Snowdrops is that we should not worry unduly about it and enjoy what plants we have.
  See below for information regarding virus elimination from plants. I do not know if any of the procedures have been carried out on Snowdrops.
  Heat treatment of twin scales, before or after bulbil production ?, in ploy bags placed in water of the appropriate temperature, may have mileage for home use.
  Only a thought, but who wants to grow an all white " South Hayes" ?

MERISTEM CULTURE---- VIRUS ELIMINATION
Meristem:
- A localized group of actively dividing cells, from which permanent tissue system, i.e., root, shoot, leaf, and flower, are derived.
Meristem culture:
- In vitro culture of a generally shiny, dome-like structure measuring less than 0.1 mm in length when excised, most often excised from the shoot apex.

Meristem tip culture
Only the meristematic dome and 1 pair of subtending leaves should be excised.
If larger pieces are taken, it is likely that the virus will be transmitted. The size of a meristem plus the subtending leaves ranges from 0.1-0.5 mm. The apical dome itself measures from 0.1-0.25 mm depending on the species. There is a balance in size. The meristem tip must be small enough to eradicate viruses and other pathogens, yet large enough to develop into a shoot. AlthouIn short, gh roots may form on the shoot directly in the same medium, often the shoot has to be transferred to another medium in order for roots to develop.
Meristem tip culture is used successfully to remove viruses, bacteria, and fungi from plants. In a majority of cases heat therapy is combined with meristem tip culture in order to produce the greatest number of plants that are “virus free”.
The term meristem, shoot tip, meristem tip are often interchanged. Here we will use the term shoot tip to refer to an apical tip ranging from 1-3 cm. The meristem is strictly the meristematic dome without any primordial leaves. The term meristem tip will be used to denote the meristem together with 1-2 primordial leaves and measuring between 0.1 and 0.5 cm in height.
In case of meristematic propagation, elimination of virus particles in explant cells is reached within a short time. In many cases meristematic cells do not contain virus particles because of non-existing vascular connection with other plant parts. For plant treatment proper meristematic apex without adjacent leaf primordia (size - 0.2-1.0 mm) is used as starting explant.

Thermotherapy /Heat treatment: Heat treatment is used in those plants in which viruses cannot be eradicated just by meristem tip culture alone.

In plant tissue cultures viruses can also be eliminated with incidence of higher temperatures (heat treatment.).In such case explants are exposed to the incidence of higher temperatures, which are not lethal for plant cells, but they are lethal for viruses. Mostly used temperature range is 50-52oC with exposition about 10-30 minutes. In case this method is applied on whole plants, lower temperatures have to be used (32-40oC) with exposition about 4 - 30 days (depends on plant species and virus type).

Chemotherapy : Virus-free plants can be also obtained when antivirus matters are added into nutrient solution (Ribavirin or 2-thiouracil).
Mostly combination of thermo-therapy and meristem culture is used for virus-free plants production (e.g., cassava, bananas, citruses, strawberry, Irish potato, apples, chrysanthemas, garlic). Heat therapy combined with meristem tip culture is able to eradicate viruses, bacteria, and fungi but does not remove viroids. Unlike viruses, viroids are RNA without a protein coat – thus they are known as ‘naked’ RNA and are very difficult to eradicate. Usually the infected plant must be destroyed.

Shoot tip grafting (STG) /Micrografting
In a number of species including those of citrus, attempts at meristem culture remained unsuccessful. As an alternative, shoot tips of 0.14-0.18 mm in length isolated aseptically from a diseased plant were grafted on to young etiolated root stock seedlings grown in vitro. STG had been used to produce virus free plants in other crops including peach, and apple.

Why virus eradication works
Several hypotheses exist to explain why heat therapy and meristem tip culture when used together are effective in eradicating viruses.
  Virus distribution is uneven in a plant and is much less in a meristem.
  Viruses cannot travel quickly enough through plasmodesmata to keep up with actively growing tip.

Plants in which virus eradication is commonly used
•   Garlic, pineapple, dahlia, cymbidium, orchid, carnation ,strawberry, hyacinth sweet potato, iris, lily, apple, cassava, ,potato, grape and ginger.

[Tim Harberd]

Hi Rollo,
   Thanks for such a comprehensive reply.. I also checked back on your earlier posts (to various threads) Seems like the best course of action is to do nothing! Panic over!! Tho’ I am tempted to try ‘cooking’ a few bulbs this summer, by way of an experiment.

Tim DH