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From: "J.E. Shields" <jshields at INDY.NET>
Subject: Plant Viruses.  Was: [ARISAEMA-L] Breeding
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Hi Henry,

No one has addressed your virus question yet, so I'll take a shot at it.

In many plant families, viruses tend to be excluded from germ cells.
Whether actively or passively, I'm not sure; but most probably passively.
Still, you can often raise virus-free plants from seed produced by
virus-infected parents.

This by itself precludes the in vivo recombination you ask about. However=,
I am not familiar with the germ cell generating process in Cactaceae, so =I
can't say whether my comments above apply to cacti.

Then there is the matter of the practical aspects of creating a recombina=nt
virus. This happens relatively easily in viruses that have multiple stran=ds
of DNA or RNA in each particle. I don't think plant viruses have that
characteristic (but I can't swear to how universal this is). Dual
infections by defective viruses could result in rescuing one or both, but
again if the viruses are defective they are not (very) infectious.

Latent viruses -- where the virus genes have been incorporated into the
host DNA -- are another matter. I'm not at all sure about the occurrence =of
latent viruses in the genomes of higher plants. It certainly happens in
microorganisms. If it occurs in plants, the latent virus would naturally =be
included in the genes of germ cells and would be transmitted to the plant=s
offspring.

Hope this helps.

Jim Shields
in cold central Indiana (USA)



At 12:25 PM 12/4/2008 -0800, you wrote:
>Has anyone heard the theory that by crossing dissimilar plants we create
>plant viruses from the unmatched genetic material?
>
>--Henry Fieldseth
>Minneapolis, Minnesota, USA, zone 4/5

*************************************************
Jim Shields             USDA Zone 5             Shields Gardens, Ltd.
P.O. Box 92             WWW:   http://www.shieldsgardens.com/
Westfield, Indiana 46074, USA
Tel. ++1-317-867-3344    or     toll-free 1-866-449-3344 in USA

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