A fungus plague has been attacking the American Chestnut tree population for over 100 years now. Scientists have been trying everything to save the tree from extinction.

I wrote about one approach back in 2009:

Virus helps save the American Chestnut tree

Really innovative idea– Infect fungal infected trees with fungus… infected with a virus. The virus infects the infecting fungus, and weakens it so the trees immune system can kill it. Very cool, but complicated.

The other idea I mentioned in that post was to cross-breed the American tree (susceptible to the fungus) with its Chinese cousin (not as susceptible to the fungus). This approach has been difficult to perfect– scientists want to get the bare minimum number of genes required from the Chinese genome, while maintaing the resistance. So, if you cross the trees once, approximately half of the offsprings genome will be Chinese chestnut, and half will be American chestnut. If you are lucky, the Chinese half will contain all the genes necessary for resistance. Then, you have to cross that offspring with another American. Approximately one quarter of the offsprings genome will be Chinese, and three-quarters American, and if you are lucky, the Chinese quarter will contain all the genes necessary for resistance. This keeps going on and on and on, until you get a tree that is 99.99999 American Chestnut, and only the fungus resistance genes from the Chinese chestnut.

This process requires a lot of time. Chestnut trees arent fruit flies. It also takes a lot of luck. Luck isnt something you want to have as a factor in your experiments, and its not something you want to rely on to keep a species alive.

Why dont we save a lot of time and take ‘luck’ out of the equation by generating a genetically modified American Chestnut tree? Just put The Right Genes into the genome of the American Chestnut?

YAY!

Transgenic American chestnuts show enhanced blight resistance and transmit the trait to T1 progeny

Heres a problem: The Chinese Chestnut tree is resistant to the pathogenic fungus thanks to numerous genes working together.

Thats not fun from a GMO perspective.

You have to get more genes in, expressed at the right levels in the right tissues, and then when that GMO tree crosses with another tree, the offspring might lose one/two/all the necessary genes. Thats not ideal.

So, these researchers took *one* gene, from wheat, that could do the same job as the seven genes from the Chinese Chestnut!

Oxalate oxidase wipes out the oxalic acid the pathogenic fungus needs to cause trouble. When oxalate oxidase was expressed in GMO chestnut leaves, it could kinda protect the leaves. Kinda. I mean it did compared to ‘wild’ American chestnut, but not nearly as well as the network of genes that protect the Chinese chestnut.

So this is not a perfect solution. Yet.

But ‘kinda’ is an extremely positive starting point. Its a position that can be improved upon in the future. This paper suggested that increasing the expression levels of oxalate oxidase might be enough to not only protect the American chestnut just as well as the natural network in Chinese chestnut, but actually push resistance beyond what is found in the Chinese Chestnut!

GMO American chestnut, like GMO papaya, might just save a species from going extinct.

Comments

  1. #1 Narad
    June 4, 2014

    like GMO papaya

    The companies had no corporate presence here on the Big Island, which lacks the large parcels of land they preferred. Still, Ms. [Margaret] Wille [of Arizona and New England] said at a ‘March Against Monsanto’ rally last spring, if the island allowed farmers to grow genetically modified crops, the companies could gain a foothold. ‘This represents nothing less than a takeover of our island,’ she told the crowd. ‘There’s a saying, “If you control the seed, you control the food; if you control the food, you control the people.”‘ …

    “Another Council member favored razing every genetically modified papaya tree on the island.”

  2. #2 Hank Roberts
    hankroberts.wordpress.com
    June 5, 2014

    > a lot of time
    40 years on, Phil Rutter (badgersett.com) has been killing vast numbers of chestnut trees year after year (a few years after planting them), doing classic mass selection for resistance and other behaviors of interest for woody agriculture. I’ve been a friend and supporter since we were teenagers, so don’t rely on me — look up his work at his site.

    Taking the trees with higher oxalate oxidase levels, the question then is whether this is a good change through the working lifetime of the tree. I asked Phil about this a few years ago and he replied:

    https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2634576/

    I’m no expert. But you might want to look at that.
    I wonder what happens to an older tree.

    He had several other thoughts but I won’t go beyond pointing to what’s published.

    This isn’t a “he’s right they’re wrong” comment, not at all — I grew up in N. Carolina in the 1950s, where the hilltops had huge blowdowns of giant dead chestnut trees, still there, not rotted away. And of course what died is the above-ground part — the root systems are mostly still there putting up new shoots in rings the diameter of the old giant trees, leafing out for a few years, then getting blighted, only very rarely producing a viable nut.

    Given enough millenia, of course, they’d come up with a resistant variation on their own, if we don’t dig them up and pave them over — but I think working to speed that along is a good idea. Everyone is pulling in something they think is the best direction; the result is the sum of all those.

  3. #4 Greenpa
    June 6, 2014

    I would suggest you REALLY need to talk to The American Chestnut Foundation; which is doing the breeding work- which has progressed, actually, to the point where the USDA Forest Service, not known as a patsy, is planting thousands of them out in the forest – NOW. The take you are getting from the “virus” people, and the “GMO” people- is very -VERY slanted in favor of their own directions, and they slant the breeding backwards as hard as the can. Think of this, though, please- ever time you go to the grocery store and buy fruit and veggies – and meat, for that matter; virtually 100 of those crops have be SUCCESSFULLY – backcrossed. Um – it WORKS. And it’s working for the trees. And no; it’s NOT slow; a generation every 3 years; and no it’s NOT “bad” to have a few extra genes from China in there. You can’t tell at all – but, have you heard? Climate is CHANGING. Now exactly why would you want a tree with genes identical to a population from 100 years ago – and no new variation? New variations = EVOLUTION, and um, survival.

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