Virus helps save the American Chestnut tree

100 years ago, American Chestnut trees grew up and down the East coast. Great wood, nommy nuts, awesome! Unfortunately, an epidemic of an Asian fungus, Cryphonectria parasitica, basically wiped them out.

Asian Chestnut trees are resistant to the Asian fungus, so theoretically we could 'save' the American chestnut industry by planting Asian trees here... but they dont have the same beneficial features of the American species.

How can we save the American Chestnut?

Solution 1 (in progress)-- Keep crossing Asian Chestnut trees with American chestnut trees until you get a tree with American characteristics and Asian fungus resistance (or take a shortcut and make a GMO).

Solution 2-- While Solution 1 is going, give currently surviving American Chestnut trees a therapeutic vaccine. Therapeutic vaccines dont prevent infection like the vaccines you are familiar with (like MMR, which prevents measles/mumps/rubella), they are given post-exposure to limit pathogenesis.

American Chestnut trees with Asian fungal lesions are given a 'vaccine' in the form of more fungus... but this fungus is infected with a fungal virus, hypoviridae. The virus goes on to infect all of the fungus infecting the tree, weakening the fungus so the trees immune system can kill it off!

Fleas on the backs of fleas!

You cant use virus/fungus as a prophylactic vaccine, as plants dont have an adaptive immune system like we do (they dont 'remember' pathogens theyve seen before). But this therapeutic 'vaccination' strategy can keep the American Chestnut population alive long enough for the breeders to find a permanent solution!


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How about a GMO in which the viral genome is inserted into the chestnut tree genome, hooked up to a wound response promoter? I.e. circumvent the carrier fungus part of the regimen.

By Bayesian Bouff… (not verified) on 16 Nov 2009 #permalink

I may be wrong here, but as I understand it the American Chestnut population is having no problem staying alive--what it has is a problem maturing. The fungus takes a while to kill, and trees will grow old enough to bear chestnuts, then die before they reach full maturity. The woods may be full of young chestnut trees (at least in places), but few or none reach maturity.

The "few" part of "few or none" is important. I seem to recall great excitement locally a few years ago when a stand of mature chestnuts was located. In addition to the groups crossing American Chestnuts with Chinese Chestnuts, there is at least one group attempting to breed pure American resistant trees.

Now someone do the same for Tanoak and Sudden Oak Death, please.

4. Optimus Primate said:

"Great. That's all we need: autistic trees."

Celebrities love trees AND autism!

Maybe we can keep Jenny McCarthy busy slapping 'toxin' absorbing pads on the trunks while Bill Maher performs Buddist chants and arboricultural acupuncture with thumbtacks.

Wait! Wait....ultimate career: Doctor of Arbochiropractic specializing in psychic Ayurvedic diagnosis of Deciduous sub-luxations of the xylem and phloem.

By Prometheus (not verified) on 16 Nov 2009 #permalink

That's very interesting. Is there any chance this will work for other plant diseases that are caused by nasty little fungus? I'm worndering in particular about Dutch Elm Disease which can be controlled but generally not eradicated once an Elm is infected.

Sorry, Rob,

Acorns ain't yummy. (Not that I particularly cared or chestnuts when I tried them. Shoulda collected some of the local ones, I s'pose.)

The virus works ok as a "vaccine" in European commercial orchards because the fungus' population biology is simpler there and it's economical to inoculate trees individually. It won't work for North American forests because (A) the fungus is diverse and has resistance to the viruses and (B) basic epidemiology indicates that a disease that kills its host quickly (as the hypovirus does) is inefficiently transmitted through a host population.

Rob: I worked in the sudden oak death community until recently. I never heard of anyone who was looking for/found a biocontrol for ramorum (or any other phytophthora for that matter), but if one exists, we'd at least benefit from an extremely homogenous pathogen population structure.

The virus goes on to infect all of the fungus infecting the tree, weakening the fungus so the trees immune system can kill it off!

Trees have an immune system?? What does it consist of?

By Rorschach (not verified) on 16 Nov 2009 #permalink

Plants have a two-staged immune system, analogous (grossly) to the animal immune system.

The base level (the innate immune system) consists of simple constitutive and generic wound responses (e.g. deposition of defensive callose). Some plants can recognize specific pathogens with R genes, which instigate a stronger, faster response that includes production of reactive oxygen species, chemical deposition and programmed cell death. Although R genes are *very* roughly analogous to antibodies, they aren't affiliated with specialized cells and do not recombine during an individuals lifetime (and are therefore much less sophisticated and less important to plant health than antibodies are to mammalian health).

Thanks Matt D, that's interesting !

By Rorschach (not verified) on 16 Nov 2009 #permalink

Matt: That's very interesting. I'd never heard of R genes before. When I took botany, all we learned about was the wound response thing. So which plants do and don't have R genes and how many different ones might an individual plant have?

By Stephen Bahl (not verified) on 16 Nov 2009 #permalink

Therapeutic vaccines dont prevent infection like the vaccines you are familiar with (like MMR, which [often] prevents measles/mumps/rubella)

There, fixed.

Therapeutic vaccines dont prevent infection like the vaccines you are familiar with (like MMR, which [often] prevents measles/mumps/rubella)

There, fixed [antivax gibberish inserted].

There, fixed.

By LanceR, JSG (not verified) on 17 Nov 2009 #permalink

I'm not up on the cutting edge of R gene work, but we have a pretty shallow understanding of them. A few specific R genes have been well characterized in model systems, and many poorly characterized ones have been used to breed increased resistance in crops, but I don't think anyone really knows what proportion of plants have them and how many R genes there are in each plant. A given R gene may only recognize one strain of one pathogen, so I imagine some plants may have lots of them. They seem to only play roles in the relatively rare case when a pathogen is able to overcome every other defense the plant has.

What about a prophylactic vaccine for the Wee Willy Fucktard virus? Anyone got one of those in their pocket?

That boy gets stupider by the comment.