Tulip virus

[mark smyth]

Have you seen Gardening Which? this month? In it it says plant Tulips in November to stop Tulip fire/virus. Isn't the virus already in the bulb?

[Maggi Young]

That's what I think, Mark.. that the virus is already present. there is another fungal disease, I think, which affects the leaves which might be prevented by early planting  ....

[Paul T]

Or else it means that you stop visible symptoms of the virus etc.  Doesn't cure the virus, but it might mean that you don't get the unsightly stripings etc?  To my knowledge you can't cure a virus!!

[rob krejzl]

Deep, late planting is suggested as a means of reducing Tulip Fire. I suppose that, perhaps, late shoot emergence might also reduce the chance of aphid attack (& thus infection). Bit of a stretch though.

[Boyed]

It is healthy to plant tulips starting from mid October, when the soil temperature decrease. This is done to prevent the bulbs from fungal desease. Besides, the bulbs have enough time to form roots, which is important for best performance and good increase.

It has nothing to do with the virus. Virus is mosly transferred by bees and aphids. The ones I grow under cold glass never catch virus, while the others in an open air do. And that is the reason that I think that mostly the bees spread the virus; though some bulb fellows don't think so.

[Maggi Young]

Greetings, Zhirair, welcome to the forum.
I agree that it is quite possible for the bees to be spreading virus as they transfer pollen.

we look forward to hearing more from you and seeing your plants.

[Maggi Young]

AAH! My apologies, Zhirair, Thomas reminds me that you are the same Zhirair who came to the old Forum! So, welcome BACK, indeed!

[tonyg]

Welcome back Zhirair - I was thinking of you the other day as I was repotting some of my bulbs, they have dome well.

Bees spreading virus - scary, especially if you include all the other pollen transferers ... even down to my cotton bud used to pollinate crocuses.  Lets hear what other people think about this idea.  Please tell me that the seeds produced are 'clean' ....

[Boyed]

Maggy, Tony,

Thanks for warm greeting.
I discussed this topic with different bulb growers and some think that virus is not transfered by bees; but I don't think so besause of my experience. I sure that bees are virus-transferers.

Tony I have been also thinking about you lately as the crocus season getting close. Your crocus niveus seeds sent to me 3 years ago grew quite big and I hope that this year I will have some blooms. Let's see. Thanks a lot.

[Martin Baxendale]

 Bees spreading virus - scary, especially if you include all the other pollen transferers ... even down to my cotton bud used to pollinate crocuses.  Lets hear what other people think about this idea.  Please tell me that the seeds produced are 'clean' [/quote]


Tony, Thomas and I were having this very discussion offline a day or two ago - can pollen carry virus?

The good news is that seed is definitely not supposed to carry virus (the fast cell growth in seed formation is supposed to be too rapid for virus infection to keep up with, in the same way as during rapid meristem cell growth in micropropagation, which can ' clean-up' virused plants like lilies for example).

The bad news is that non-one I've talked to about it knows if pollen can carry virus.

Personally, my gut feeling is that it shouldn't, as the cell growth involved in pollen production is, just as in seed production and micropropagation, very fast and involves very small amounts of biological matter, so viruses should have a hard time getting into pollen.

The one thing that could happen I suppose is that the sticky pollen-receptive stuff from the stigma of a plant could be transferred to another plant's stigma accidentally, and that could well transmit virus. So when hand-pollinating, it it's probably best to sterilise your brush between pollinations (or discard your cotton bud, Tony) though I would think this would only be a serious risk where the plant produces a lot of sticky stigma juices. I don't bother with this when pollinating snowdrops. I just give the brush bristles a good flicking and a rub on my sleeve to remove pollen.

But the possibility that pollen might transfer virus still worries me. Especially when cross-pollinating rare snowdrops. Anthony seems quite clued-up on biological processes, so maybe he can give us his opinion? (incidentally, Anthony, I've always assumed from your posts that you teach biology or a related subject. Is that right?)   

[Joakim B]

Without being an expert I think that the pollen in plants are "only half the dna" and that that might influence it as a producer of virus if infected.
I think that for humans it is not the pollen it self (spermcell) that is spreading the virus but the juces? I am not sure about it. But google on cleaning sperm from HIV would give the answer and mayby then it also aplies to plants. Blooms and bees as it is called in Swedish since I do not get "birds and bees" as it is in English.
This gives credit to Martins idea of stigma spreding to other stigma rather than the pollen itself.

Just speculations from my side
Kind regards
Joakim

[tonyg]

Thanks guys for the clarification.  Great thing about this forum - an informed response is often there when you need it!

[ashley]

At least some viruses can be transmitted between some plants via pollen and seed.  E.g. Under Plant Viruses at Wikipedia:

‘Plant virus transmission from generation to generation occurs in about 20% of plant viruses. When viruses are transmitted by seeds, the seed is infected in the generative cells and the virus is maintained in the germ cells and sometimes, but less often, in the seed coat. When the growth and development of plants is delayed because of situations like unfavourable weather, there is an increase in the amount of virus infections in seeds. There does not seem to be a correlation between the location of the seed on the plant and its chances of being infected.  Little is known about the mechanisms involved in the transmission of plant viruses via seeds, although it is known that it is environmentally influenced and that seed transmission occurs because of a direct invasion of the embryo via the ovule or by an indirect route with an attack on the embryo mediated by infected gametes.  These processes can occur concurrently or separately depending on the host plant. It is unknown how the virus is able to directly invade and cross the embryo and boundary between the parental and progeny generations in the ovule.  Many plants species can be infected through seeds including but not limited to the families Leguminoseae, Solanacease, Compositae, Rosaceae, Curcurbitaceae, Gramineae.’

For obvious reasons most research on this has focussed on commercial crops, particularly Prunus.  Apart from vertical transmission (parent to offspring) via pollen and seed, horizontal transmission from infected pollen falling on insect-damaged plant tissues can also happen.

[Martin Baxendale]

That's interesting, Ashley. It fits with fast cell growth outpacing virus infection - in cold weather, cell growth and development of pollen, ovules and fertilised seeds is all lilkely to be much slower than in warm weather (especially relevant for bulbs that flower in winter and early spring) so in such adverse (cold) weather there's more chance of a virus catching up with cell growth and infecting. In micropropagation, of course they keep the temperature optimum for cell growth.

There must have been some new research done on this. But it looks like not all viruses are able to infect seed, pollen and ovules. If only 20% of those studied so far in edible crop plants can do it (and even then only if the weather is cold) then at least we have a fighting chance - in that it may not be very common in bulbs. Even so, it's still worrying and indicates that care does need to be taken with pollen transfer, especially with avoiding using pollen from plants and bulbs known  to be virus infected or showing symptoms (which I have tried to avoid for this very reason, just in case).

[ashley]

Hi Martin.  Yes it's an interesting subject.  Presumably virus infection only matters if it impairs plant performance (incl. appearance).  As more genomes are sequenced, virus (and indeed bacterial) genes or parts of genes integrated into host DNA are turning up surprisingly often.  Therefore they must either confer selective advantage or at least be relatively harmless to the host.  Of course this begins to blur the distinction between pathogen and 'victim'!