American Chestnut trees found in GA   Will Blozan
  Jul 01, 2006 08:22 PDT 

What the $#%^?

Trees like those described in NH are not hard to find down here. A large
20-30 year old tree is not a resistant tree, just a lucky stump sprout. It
is the same genetic material that was KILLED in the first place. I think the
reporter meant to say "NORTHERN-most flowering specimen..."

I cored a selection of chestnuts when I worked for the national park service
and every one was approximately 38-43 years old at BH. Diameters ranged from
2" to 16". Trees (3rd generation stump sprouts) older than those in NH are
very common in the southern Appalachians. The largest trees like the one I
climbed a few years ago to pollinate for the ACF are likely only 20-25 years
old.

I seriously don't understand the significant of the find. Can anyone clue me
in?

Will

-----Original Message-----
From: edniz
Sent: Saturday, July 01, 2006 7:50 AM
Subject: Fw: American Chestnut trees found in GA


Hello,
        Here is an article from Yahoo news of finding healthy American
Chestnuts in New Hampshire:
http://news.yahoo.com/s/ap/20060618/ap_on_sc/chestnut_trees

        I received another message from a friend of mine in Cooperative
Extension of a chestnut find in Georgia:
  May 19, 2006" By Elliott Minor, Associated Press

ALBANY, Ga." A stand of American chestnut trees that somehow escaped a
blight that killed off nearly all their kind in the early 1900s has been
discovered along a hiking trail not far from President Franklin D.
Roosevelt's Little White House at Warm Springs.

The find has stirred excitement among those working to restore the American chestnut, and raised hopes that scientists might be able to use the pollen
to breed hardier chestnut trees.

"There's something about this place that has allowed them to endure the
blight," said Nathan Klaus, a biologist with the Georgia Department of
Natural Resources who spotted the trees. "It's either that these trees are
able to resist the blight, which is unlikely, or Pine Mountain has
something unique that is giving these trees resistance."...

"The largest of the half-dozen or so trees is about 40 feet tall and 20 to 30 years old, and is believed to be the southernmost American chestnut discovered so far that is capable of flowering and producing nuts..."

Source: Associated Press
Re: American Chestnut trees found in GA   Randy Brown
  Jul 01, 2006 10:57 PDT 

Just as a tangential, off the cuff thought. How do we know the
native virulence (excluding hypovirulence) of the blight has remained
constant over time?   The Chestnut's gene pool may be 'frozen in
time' but the fungus isn't. Generally it's not in a disease's best
interest to eliminate it's host.

As a example, the virulence of syphilis declined rapidly in the human
population:

"The first well-recorded outbreak of what we know as syphilis
occurred in Naples in 1494....   ...The disease swept across Europe
from its early epicenter at Naples. The early form was much more
virulent than the disease of today, the incubation period was
shorter, only a few months, and the symptoms were more severe. In
addition, the disease was more frequently fatal than it is today. By
1546, the disease had evolved into the form we know now."

http://en.wikipedia.org/wiki/Syphilis_disease

Any thoughts?
RE: American Chestnut trees found in GA- HUH???   Edward Frank
  Jul 05, 2006 18:05 PDT 

Randy,

This is an interesting idea that I have not heard discussed before: [the
virulence of the blight potentially may have changed over time.] I don't
know what to say. Certainly the potential is there but I am not sure
how rapidly the fungus involved may have evolved and am not sure how to
test the hypothesis. Maybe someone else has some ideas.

A second question comes to mind concerning the interaction of the blight
and the chestnut. Some of the trees were killed completely - dead from
top to root. Others continue to sprout new shoots from the roots 80
years later. They have survived in a fashion. So the blight was not
100% deadly - just slightly less. You can see in some plants, when
subject to grazing by insects or animals a change in leaf chemistry
takes place. The first leaf may have be delicious, but sibsequent
leaves may become progressively more distasteful or even poisonous with
continued predation. There is a potential to produce these chemicals in
the leaves, but it takes time for the plants to adapt to exhibit the
characteristic. The death of these chestnut trees was relatively rapid.
Perhaps they had a potential to resist the blight, but because of the
speed of death, this potential was not able to be developed or
exhibited. With the chestnut trees sprouting over and over again, has
there been any change in the ability of the tree species to resist
diseases like blight over time? Perhaps given time, these resprouts,
the maximum potential of the tree to resist disease can eventually be
realized, and the offspring of these trees could be more resistant to
blight. I am not talking Lamarkian aquisition of traits, but
development of a potential within the pre-exisitng gene pool.

Comments?

Ed Frank
RE: American Chestnut trees found in GA- HUH???   James Smith
  Jul 05, 2006 20:01 PDT 

There must certainly be examples of diseases that have managed to wipe
out the host populations. Just because it's not terribly logical--even
in an implacable evolutionary way--doesn't mean that an organisim
wouldn't capitalise on a host's weaknesses to completely wipe them out.
I know almost nothing about the subject, but I would assume that thing
like that have occurred over the course of the history of life on Earth.

On the other hand, hasn't the balsam wooly adelgid shown signs that it's
not as effective on the trees in the Smokies and Blacks? Aren't the
newer generations of balsam trees coping with the introduced pests? Or
is it merely because the adelgids prefer older trees? Or did the
adelgids die off after the initial onslaught when almost all of our
balsam forests were destroyed?

If the balsam trees are, indeed, showing more resistance to the balsam
wooly adelgid, perhaps this bodes well for the eastern and carolina
hemlock species. Perhaps after they are initially wiped out, a newer
generation will be more likely to resist the pest.

Hasn't it been conjectured that a feline virus almost wiped out the
cheetah? Haven't genetic tests shown that at some time in the past the
breeding population of the entire species was reduced to just a few
dozen individuals? If so, then that would be an example of a disease
coming pretty darned close to completely wiping out a host.
RE: American Chestnut trees found in GA- HUH???   wad-@comcast.net
  Jul 06, 2006 06:04 PDT 
ENTS

I have always felt that the chestnut would regain it's glory sometime, because it did not die altogether. It may build resistance over time, or the fungus may change and become less powerful. I imagine these things take hundreds, if not thousands of years. Although DNA does mutate over time, I often think that a population is whittled down to those that have the resistant DNA, and then the species has to repopulate from that core group. Similar to humans and the Black Plague.

The two trees I went to look at in SE Pa turned out to be Chinese, or at least hybrids of some kind. The gentleman from the Chestnut foundation took samples, and will let me know. I thought the leaves looked to be chinese, but the habit was single stem, which threw me off. That and an owner swearing they were american.

Unless a Chestnut is found on the East Coast that is over 75' tall, and has been injected with the fungus and lived, I won't be convinced of any of these new discoveries. I hope that it happens in my lifetime, and I will continue to plant chestnuts each year.

Scott
Re: RE: American Chestnut trees found in GA- HUH???   brown_-@colstate.edu
  Jul 06, 2006 08:16 PDT 

I recall seeing a chestnut with abundant sprouts 10-15 years ago in SE
PA
(unforunately the farmer has since expanded his pasture and it is
gone).
However, that stump had several sprouts including one about 15-16" dbh
that was producing mast. It also had numerous older sprouts that were
dead but were generally smaller, in my recollection. It seems possible
that the stump-sprouts were getting larger over time for whatever
reason.

Roger Brown
RE: American Chestnut Resistance   Edward Frank
  Jul 06, 2006 19:35 PDT 

Roger, James, Scott, everyone,

All of this talk of the American Chestnut recovery is still just speculation
on my part. The possibility that these things are happening is there, but
there is no real evidence that any of this has actually or is actually
taking place.

We don't know if the blight has or has not changed in virulence. Evolution
in lower organisms like fungi and bacteria is very rapid. We could have
had thousands of generations of the blight since its introduction. The
point that it isn't good for an organism to kill its host is true to a
degree. If the disease spreads to another target before the host dies then
it just lowers the spreading rate but does not break the cycle.    This was
an introduced organism, and in its native habitat it does not kill the trees
because of their natural resistance. Then if it is introduced into a
different environment with little to no resistance, the blight could kill
all of its hosts before a chance to evolve into a less resistant variety
occurs. Killing the host would be a misdirection as the organism first
evolved - how could it establish itself effectively to spread the initial
mutation?- but once it has evolved and is introduced into a different
population, that restraint is gone. It would be the typical boom and bust
population growth pattern. The boom spreads across the entire population,
then with the bust all of the host trees die and the blight population is
trivial until a mature tree grows for it to infect. I would be more
optimistic of the American chestnut developing a genetically resistant
strain if a small percentage of the mature trees initially infected had
survived. I don't know of any at all that survived beyond the root sprouts.

There may be been several genetic strains introduced at once, rather than a
single strain. That would make it harder for resistance to develop or for
the organism itself to mutate or evolve into a less virulent strain. We are
better at epidemiology now that we were back in the twenties. It may have
been done already, but I would be interested in seeing a detailed analysis
of the spread of the blight using modern computer modeling techniques. It
may be difficult because I am not sure all of the necessary infection data
was collected in a useful format for the models.

Say there was more than one strain of blight, each tree could be infected by
more than one strain. Alternatively if there were an evolution of a strain,
each tree could be infected by both descendents of the original strain and
the evolved strain. If the infection pattern was random, then the greatest
differentiation of the individual strains would be in areas farthest from
the initial infection in terms of physical distance and time of infection.
(This pattern is the same structure as occurs in various random walk
groundwater contamination flow models). Samples of the blight from infected
sprouts from different areas of the range of the blight and chestnut could
be genetically analyzed to see if there is any difference. If there has
been some shift genetically in the American chestnut (unlikely), or if the
ones sprouting new growths are similar to each other and different from the
initial stock genetically, that also could be determined. There are
chestnut trees growing outside the former native range of the American
chestnut that could be sampled for a base of the original population. The
national champion is growing in Washington state.

The analogy with the human disease is flawed to a degree - not as a starting
point for consideration - but as far as the disease spreads. In the human
infection an individual is likely to have been infected by a single strain
and then passes on that same strain. Not always, but commonly. Thus any
change in virulence would be passed on and preserved. A tree may be exposed
over and over again to a variety of different strains (if any) and then
these are passed on indiscriminately to oath trees. A less virulent strain
would not be any more likely to be passed on to other trees, over a deadly
one, unless it was the only strain present. The process is less selective
and less likely to rapidly evolve a less deadly strain. Again given random
infection spread from tree to tree, the trees farthest away would be most
likely to have a blight monoculture, if multiple strains were present.

Just rambling on...

Ed Frank
Re: American Chestnut trees found in GA- HUH???   Randy Brown
  Jul 06, 2006 19:35 PDT 
Ed,

I guess the reason I asked is the renewed efforts to find chestnuts
has turned up quite a few trees. 20-30-40 years old.
For example:
http://www2.vscc.cc.tn.us/jschibig/resurrectingthechestnut.htm
(Scott: They claim tree from Adair County is old enough to have
survived the initial wave)

If memory serves, Kentucky and Tennessee were completely blighted by
1940's.   So If one had looked in 60's & 70's
would one have found a similar number of surviving young trees?   Or
is it simply a matter of finding more trees then we expected
simply because we are finally bothering to look?

Another factoid that got me thinking in this direction is the
difficulty with introducing hypovirulence because of the diversity
of the fungus here in America vs Europe. Begs the question whether
this diversity arose on this continent or whether the many
different strains were introduced multiple times. This link seems to
suggest it may have been introduced multiple times

http://www.caes.state.ct.us/FactSheetFiles/PlantPathology/fspp008f.htm

Perhaps this is just an academic question now, but looking down the
road when the various breading programs introduce
resistant trees back into the wild, it then falls into our hands to
determine how much genetic diversity we are going to preserve.
I have a hard time believing that the introduced resistants and the
susceptible native population will interbreed significantly
because the susceptible trees flower so rarely. At the same time, I
don't see how the susceptible trees can persist
when faced with the competition from the resistant trees.

The ACF is looking to expand its breeding program so that each state
can breed it's own regional varieties. It's a nice step,
but how do we know when to draw the line? 3-4 exceptionally
resistant trees per region? Or a large pool of perhaps dozens of
not-so-resistant trees just to cover the unknowns and perhaps rely on
natural biological trends to fill the resistance gap?

Just some idle speculative, and perhaps ignorant questions.

Randy
RE: American Chestnut trees found in GA- HUH???   Matthew Hannum
  Jul 08, 2006 11:18 PDT 

In the long run, assuming that the ACF's trees succeed and are able to
begin repopulating the woods with blight-resistant chestnuts on their
own, I think it will fall to nature to decide what happens to whatever
chestnuts that remain before the blight. Once enough blight-resistant
genetic material is introduced, the non-resistant trees will vanish over
the years from competition, but I don't see any way to prevent this, nor
am I sure it would make much of a difference provided that there are
enough variations of the blight resistant trees out there and that they
can spread on their own through the woods while maintaining that
resistance.

The blight may change and throw a wrench in the plans of course, but
nobody really knows how that would work out, though I do agree that it
is not an evolutionary improvement for the blight to mutant into new
lethal forms. I suspect in the long run we'll have less lethal blight
and blight resistant trees, although the non-resistant trees that have
survived to this day may never amount to much of anything after catching
the blight.
Re: American Chestnut trees found in GA- HUH???   Jess Riddle
  Jul 10, 2006 07:27 PDT 

Ed,

As far as I know, the survival of some chestnut root systems and not
other is entirely environmental. Root systems that do not produce
sprouts typically occur on heavily shaded sites. The shade usually
comes from a thick heath shurb layer or from the multi-layered canopy
of a cove forest. A soil organism, I don't know the name, protects
the roots of chestnut from the blight. Perhaps the patterns of sprout
survival are different in other parts of the country, but the above
patterns are fairly consistent in the southeast.

The potential for a delayed chemical response is interesting and one I
had not considered before. However, I think that kind of resistance
is unlikely. First, that building response to attack would have a
genetic base and have to have evolved as a response to some
environmental pressure. Maybe some other fungus would have supplied
that effective pressure, but in that case it seems like someone should
have noticed the response before. Second, I think that chemical
response usually involves herbaceous plants or the herbaceous parts of
woody plants. A tree responding in that fashion would lose a huge
energy investment, the trunk, and access to resources. A faster
response would allow much greater reproduction and hence be selected
for. Third, the tree while only partially infected would have much
greater resources to fight back with than a new sprout drawing on
energy reserves stored in the roots. I'm just speculating here, and
don't know if the process occurs in reality.

Jess Riddle