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  Variegation and viruses
From: Steve Marak samarak at arachne.uark.edu> on 2002.03.03 at 20:39:04(8245)
Plant viruses seem to be the subject of as much interest and concern, and
in some cases paranoia and misinformation as computer viruses. They come
up regularly on two other lists I'm on, and occasionally elsewhere.

Obviously, they do exist and do damage, in some cases (TMV) serious
economic damage. Every serious orchid grower I know takes a variety of
precautions. (If only they took the same degree of precaution against
computer viruses!)

John, I am not an expert but I do recall a study of variegated plants
which showed that the vast majority are not the result of any disease but
are rather "chimeras", multiple cell lines growing and dividing in the
plant, one of which is colored differently than the other. There is an
excellent discussion of variegation out on the net, if memory serves on
the TAMU web site (Texas A&M University, where there is a lot of good
botanical and horticultural information.)

There was also some discussion of the old Rembrandt type tulips, which did
have a virus (some unimaginative name like "tulip color-break virus", I
think), and the newer, non-virused tulips which are now being sold. The
breeders have gone to great lengths to produce tulips which look similar
to the old virused ones, and also to ensure that none of their stocks are
virused. (There are a few die-hards who feel the new varieties just don't
have the same subtlety of color, and still grow the old virused ones. No
reputable grower will sell one, of course, so they have to keep them alive
themselves.)

As far as I know, you're correct in that there is no cure for a virused
plant. Practically everyone recommends destroying it.

But - harking back to the paranoia I mentioned earlier - do be sure a
plant really is virused before you sentence it to death. As with computer
viruses, there seems often to be a rush to judgement.

On another list a while back, a grower and breeder decided to give away
his collection. It was a valuable one, representing years of work.
However, somehow someone heard a rumor that "his collection is virused".
The rumor surfaced on that list. Suddenly, with no real evidence, people
were rushing to destroy not just the plants they'd gotten from the grower,
but even ones which had been near them, despite the counsel of cooler
heads. Someone took samples and had them tested (one of the difficulties
with plant viruses is that knowing for sure requires testing). Result: no
sign of virus in any of the samples.

Steve

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From: Paul Tyerman ptyerman at ozemail.com.au> on 2002.03.04 at 07:46:28(8246)
>
>On another list a while back, a grower and breeder decided to give away
>his collection. It was a valuable one, representing years of work.
>However, somehow someone heard a rumor that "his collection is virused".
>The rumor surfaced on that list. Suddenly, with no real evidence, people
>were rushing to destroy not just the plants they'd gotten from the grower,
>but even ones which had been near them, despite the counsel of cooler
>heads. Someone took samples and had them tested (one of the difficulties
>with plant viruses is that knowing for sure requires testing). Result: no
>sign of virus in any of the samples.
>

Steve,

I think I remember that particular episode. Sad is definitely the case!!
>From what I know you're right in that there are virus and natural
variegation in plants. The other thing to watch out for is that there are
plants where BOTH occur in the species, so you need to be sure which you've
got before condemning it to death. From memory there are two different
types of variegation in Abutilons (Chinese Lanterns.... I realise that
these are NOT aroids ). One is a genetic variegation and the other
is a viral. The viral form will jump to other Abutilons in the garden
while the genetic will not. Needless to say I removed the fairly newly
purchased variety that was a virus-based variegation (and is sold happily
in nurseries). I didn't take the step of ripping out the 7 foot high red
Abutilon next to it, and there has never been any evidence that I should
have. Knee-jerk reactions are a good way to throw out some wonderful and
healthy plants.

To my way of thinking. If you are concerned.... Isolate it!!!!! If you're
still not sure then take a "throwaway" plant and put it next to it, even
mix sap from or graft the suspected "virused" plant onto the hose that is
expendable. That is an easy way to find out whether it will spread or not.

Cheers.

Paul Tyerman

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