Hopes for Chestnut Revival Growing

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Re: Hopes for Chestnut Revival Growing

Post by Chris » Fri Aug 31, 2012 10:25 pm

Well, we shouldn't limit discussion to "mega animals". Wherever people go, we change the environment to suit "our needs". This is a hallmark of our species. These changes can impact things that weren't even directly hunted or killed for food. Also, it is easier to find the remains of giants sloths, then small rodents, let alone insects or bacteria, so we simply don't know what occurred to most living things thousands of years. More recent non-European, Polynesian first constant caused an estimated 1,000 birds species to go extinct (1/10 of all species), with some islands losing all non-pelagic birds. Hawaii lost ~ 75 of a total of ~135 species before the arrival of Europeans [that caused another 25 lost]. New Zealand has lost like 50% of all species.

Of course, unlike first Native people in America hunting large mammals and causing extincts they weren't aware of, we KNOW we are doing this.

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Re: Hopes for Chestnut Revival Growing

Post by jamesrobertsmith » Sat Sep 01, 2012 6:12 am

And when New Zealand lost so many bird species, among them were the islands' megafauna, all of the moas, the Haast's eagle, etc.


Re: Hopes for Chestnut Revival Growing

Post by Joe » Sat Sep 01, 2012 7:57 am

Chris wrote:Wherever people go, we change the environment to suit "our needs". This is a hallmark of our species.
Now, if only we can realize that our needs include a healthy, stable planet! Well, of course, some people have risen to that level of awareness, the majority have not.

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Re: Hopes for Chestnut Revival Growing

Post by Ashe County » Mon Mar 18, 2013 10:57 am

I can't get too excited about missing the megafauna, they have been gone so long. But the thought of just missing a Carolina Parakeet or Ivory Billed Woodpecker, or a big Chestnut forest for that matter, is a dissappointment. Not as big a dissappointment as was returning east and finding that the Hemlock of my youth is joining the ranks of the dead tho.

As to the Chestnut I'd sure like to have a few of those 15/16 backcrosses. ACF will sell you some nuts for a donation of 150.00 each as I recall. I'm still tempted but so far haven't signed up. It seems that even if the backcross nuts are successful that the chestnut gall wasp, also introduced, may prevent the return of chestnut forests. they don't have an answer for that one that I can find.

In the grand scheme of human impact on the species of this planet, we ain't seen nuthin yet I'm afraid.


Re: Hopes for Chestnut Revival Growing

Post by Joe » Mon Mar 18, 2013 11:10 am

I'm looking forward to watching my three 15/16 backcrosses growing this year- their third year in my lawn. I fantasize what they'll look like a century from now. I intend to measure and record their annual growth.

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Re: Hopes for Chestnut Revival Growing

Post by Rand » Mon Mar 18, 2013 10:19 pm

The ACF have done testing over the last two seasons on their 'Restoration Chestnut 1.0' (15/16 - B3F3 hybrid). They use two strains of the fungus. A virulent strain - EP155 and a weak strain - SG2-3. Essentially they inoculate the trunk and then measure how much the canker grows over the season. I've charted the results according to the percentage of each size class the tested trees fall. Basically, tall bars to the far left = Good. Tall bars to the right = Bad.

On interesting thing they note is that cool, wet weather is not favorable to the fungus (summer 2011), which probably explains such things as the successful introduction of hypo-virulence in Michigan and the relatively large size of the chestnuts at Tracy Ridge in the Allegheny NF.

(Note the sample size of the B3F3's were 300-500, but the American and Chinese were only 10-20)
Soooo.... A useful increase in resistance, but only a small percentage seem to show a resistance comparable to their chinese ancestors. Somehow I don't think this was the magic they were looking for. I visited their research farm this fall and they gave me a nice tour. They are doing massive plantings of B3F3 for another round of inter-crossing (in the thousands). Out of blocks of 150 trees they are planning on keeping 2 after testing for resistance. The selectees progeny will hopefully be what everyone is hoping for.

Their magazine has this rather circumspect assessment:
Not all backcross F2 and backcross F3 chestnut trees that have cankers as small as Chinese chestnut in the first season of canker expansion survive as well as Chinese chestnut. This has been discussed previously for earlier generations of crossing, and is illustrated for Restoration Chestnut 1.0 trees in Table 5. For instance, 32 of 87 B3-F3 in the smallest canker size class in Table 5 died between 2011 and the end of 2012. Canker lengths in any one growing season are a metric we use to assess blight resistance, but are not perfectly correlated with the underlying trait. For one thing, as we have seen above, they depend strongly on the season. This seasonal dependance is one reason we wait until the second season of canker expansion has begun before making the final selection for blight resistance in straight backcross. However, in the second season, factors that affect tree vigor start to influence canker expansion, so length becomes less correlated with genetic resistance as measured by correlations with molecular markers. So we are left with canker expansion during the first season as the source of the best metrics of blight resistance, despite its imperfections.

Canker length is strongly correlated with survival, but survival can extend to trees with intermediate canker sizes and intermediate levels of blight resistance, such as F1 hybrids. This is illustrated in Table 5, but also in plantings made by the Connecticut Agricultural Experimental Station that have living F1s more than 60 years old, still with their original stem. Those include plantings in forested as well as orchard settings. Therefore, based on current data, we can project that many B3F3 Restoration Chestnut 1.0 will survive for extended times. They should be able to resume evolving. That in itself will be a victory; the species will have a chance of persisting, and further improvement need not be carried out in the nursery or orchard, but rather in the forest; it will be rather akin to releasing captive-bred condors back into the wild. But will the B3-F3's become dominant forest trees and how many willl do so? That question will have to be answered by the progeny tests conducted in the forest. Long time periods are required to answer some of these questions, making it imperative to have started forest progeny test now, as we have

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Re: Hopes for Chestnut Revival Growing

Post by jclarke » Sun Oct 30, 2016 4:59 pm

It's rainy and I'm in the house instead of where I'd like to be, so keep that in mind, grin.
It's colder and wetter here than a lot of places, so blight will grow slower, I hope. Those BC1's, hybrid crossed back to americans, will all have chinese traits, but some will not get a copy of all the blight resistance genes. Under low blight pressure, cold, wet, whatever slows blight down, these will live. Only the ones with NO copies of the resistance genes croak right away. I'm going to make this up, for an example, so don't take it literally. Say there are 3 pairs of resistance genes, and more than one allele at each locus, say a pure chinese is AA1/BB1/CC2
or different alleles at A, B and C. Hybrids are A or A1 and a from the american, B or B1 and b, from the american, and C or C2 with c from the american. When you backcross, some will get two a's, no resistance there, two b's, same, no resistance, and two c's, not any better. Where you run into a little resistance is Aa,Bb and cc, or aa,Bb and Cc etc. What you need is some blight pressure, and a whole lot of numbers. Mass selection, in a woods setting, would cull out the aa,bb and cc individuals, but if the climate will allow low levels of blight resistance individuals to produce seednuts for even a few years, those trees pass on the A's, B's and C's needed. I can't do that here, as there is no blight here yet. I am however, mailing away the few BC1's I can produce on very young trees. Could we all do this? If BC1's have all the A,B and C's we need, and if they went in huge numbers to areas with slow blight growth, could they set seed and could nature concentrate the resistance genes over the decades? Some trees would have the chinese characteristics without the resistance, but they should get overtopped and shaded out eventually. What are other folks doing?

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