Curing virused vines?

I've just read some exciting news in the December/January issue of New Zealand Winegrower (yes, I know it's taken me a while to get around to reading it!! :-)

Some work being done by doctoral student Elaine Chan, Mike Pearson of the University of Auckland and Robin MacDiarmid of Plant and Food Research (pages 80-82) suggests that it might be possible to cure vines of virus diseases, or at least, be able to prevent virus from spreading from the infection point.

Viruses such as Grapevine Leafroll are major issues to grapegrowers around the world, so the thought that this might be able to be done is pretty fantastic! At the moment, infected vines are pulled out and replaced, and in some cases, the vines next to the infected one are removed as well, to lessen the possibility it may spread.

If researchers can figure out how to get plants to ramp up a defense mechanism against viruses, much as animals do, then the implications for grapegrowers would be tremendous (perhaps both pro and con!).

The idea is to duplicate the action of a protein in animals that signals the presence of viral agents. That protein would tell the surrounding tissue to stop making proteins, which the virus needs in order to replicate itself and spread through the rest of the plant. If that was done, then the plant could use other means to stop the virus from spreading from the infection point, say, by a hypersensitive response, where the tissue immediately surrounding the infection point dies, thereby isolating the virus. This response is well known in the area of fungal infections, for example.

They are also mooting the possibility that a plant equivalent of interferon could be developed, which would stimulate the plant to produce more of these signalling proteins and therefore stop the virus in its tracks.

These are not new ideas (see this article "Is there a plant interferon?"), but it's interesting to see that people are looking at this from the standpoint of grapevines.

If, and it's still a big "if" at this point, this was able to be accomplished, vines would be able to stop infection before it started, and infected vines could be cleansed of existing infection.  It remains to be seen if such a thing could be done with today's vines, or if new vines would need to be developed which have this capability.

As well, sometimes viruses can help to make better quality wine. The Mendoza clone of Chardonnay, for example, is thought to produce lots of the smaller berries it's well known for because it is infected with a mild strain of Leafroll virus. I'm sure there are other instances where the virus (or related "disease" organisms) may be holding back the natural vigour of vines, or changing the fruit morphology in some way that led to a clonal selection. Sometimes, you have to take the good with the bad!!