SAVING THE AMERICAN CHESTNUT AND BUTTERNUT TREE

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SAVING THE AMERICAN CHESTNUT AND BUTTERNUT TREE

• TRISTATE FOREST STEWARDSHIP CONFERENCE
• March 8, 2008
• Larry R. Severeid

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CAN THEY BE SAVED?
American chestnut
American butternut
Castanea dentata
Juglans Cinerea
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NATURAL RANGE OF CHESTNUT AND BUTTERNUT
CHESTNUT
BUTTERNUT
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ORIGIN OF THE SPECIES CONTINENT CASTAN
EA JUGLANS North America AMERICAN
CHESTNUT Eastern black walnut Chinquapin Butte
rnut Texas walnut Arizona
walnut California walnut Hinds walnut
(California) Europe(Persia) European
Chestnut Persian walnut (Carpathian) Asia Japa
nese Chestnut Japanese walnut (Heart
nut) Chinese Chestnut Manchurian
walnut Chinese Chinquapin

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History Of These Parasitic Fungi
Chestnut Butternut THE FUNGUS Cryphonectria
parasitica Sirococcus clavigigenti-
juglandacearum MODE OF DISTRUCTION Disrupts the
vascular cambium Disrupts the vascular
cambium YEAR OF DISCOVERY 1904 1967 INTRODUCED
FROM Asia Probably Asia Source of
introduction Chinese chestnut tree or
Uncertain, but it probably came from the
Japanese chestnut tree Japanese walnut tree.
(the heart nut) MODE OF
SPREAD Spores- sexual and asexual Spores-
asexual only Present situation No blight
resistant American There are trees that
appear to be blight chestnut has been
identified. resistant, but more studies are
required.
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THE MIGHTY CHESTNUT
At the turn of the 20th century it dominated the
eastern deciduous forest. There were over 4
billion chestnut trees that constituted 25 of
the trees in the 2,000,000 acre forest
range. Its prolific annual nut production
sustained a large animal population, including
deer, turkey, black bear, mice, squirrels and
domestic hogs. The valuable nuts were also
gathered and used by people. The bark and wood
were rich in tannin and it was the primary
source of tannic acid used to process leather.
The by-product pulp was used for making paper.
The wood was rot resistant, light in weight,
straight grained and resisted warping. It was
ideal for lumber, fence posts, split rail fences,
rail road ties, and telegraph poles. It grew
incredibly fast, was able to live 300 years and
began producing seed as early as 8 years of
age.
American chestnut
Castanea dentata
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THE CHESTNUT CANKER
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THE WHITE WALNUT
The range of butternut and black walnut overlaps
but the butternut extends further north and is
more winter hardy than the black walnut. The
typical tree has a short life expectancy of
around 75 years. Its seed-bearing age begins at
around 20 years. The tree is shade intolerant
and typically does not dominate a forest stand
but rather grows sparsely. Forest grown
butternut that are competing for sun grow
straight and make excellent
lumber and veneer. Butternut wood
was used for trim, paneling and furniture. The
nutmeat is oily and too rich to eat alone,
however it is used in cooking. It is prized by
squirrels.
American butternut
Juglans Cinerea
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BUTTERNUT CANKER
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STRATEGIES FOR RESTORING THE CHESTNUT

• Breeding with surviving American chestnut
  populations.
• Hybridization with Asian chestnuts. (early
  programs)
• Backcross Breeding Program
• (American Chestnut Foundation)
• Transgenic Manipulation
• Introduction of hypovirulent fungi
  (Hypovirulence)

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BACKCROSS STRATEGY(THE AMERICAN CHESTNUT
FOUNDATION)

• In 1982, the foundation was established because
  of a vision of two men, Charles Burnham, a noted
  geneticist, and Phil Rutter, an evolutionary
  ecologist. They were sure that the American
  chestnut could be restored.
• These Minnesotans were convinced that the
  American chestnut could be saved by applying the
  same principles that had been successful in
  breeding plants. This method, back crossing, was
  used to transfer a single hereditary trait among
  interbreeding species. The desired trait was
  blight resistance and the species were the
  American chestnut and the blight resistant Asian
  chestnuts.
• The big difference was the time scale. To
  achieve their desired objective, it could take
  over 25 years. What institution would have that
  kind of attention span?
• They concluded that only a private, self funded
  foundation would remain focused and stead-fast in
  achieving such an objective. A board (primarily
  mid-westerners) was assembled and in 1983 they
  first met. The first foundation meeting was on
  September 22, 1984. The rest is history and the
  Foundation presently has 7000 members. There are
  15 state chapters, University, State, and Federal
  affiliates. A research center was established in
  Virginia in 1989 and has remained the prime
  coordinator of the reseach activities, especially
  the back cross program.

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BC3 F2 ORCHARD

The seeds were procured from the American
Chestnut Foundation and it had taken 25 years to
achieve the desired genetic objectives, 93
American genes and 7 Chinese genes which
hopefully includes the genes for blight
resistance. Those trees that show poor
resistance to the Cryphonectria inoculation or
that do not have the physical characteristics of
the American chestnut will be eliminated.
The remaining trees will eventually cross
pollinate and the resultant seed will become BC3
F3 trees and should be resistant to the blight.
The fence posts surrounding the orchard are
American chestnut.
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TRANSGENIC APPROACH

• The ideal transgenic transfer would be to
  identify and isolate the 3 genes of resistance
  from the Asian chestnuts and insert them into the
  American chestnut. These genes have not yet been
  isolated but research centers are working to
  isolate them.
• Presently, scientists are testing a gene obtained
  from wheat, that is also found in many grasses.
  This gene produces (encodes) an enzyme, oxalic
  oxidase, that breaks down oxalic acid (oxalate).
  The blight fungus produces oxalic acid along the
  margin of the canker, disrupting the trees
  defenses. There is early evidence that this
  introduced gene enhances the trees ability to
  resist the progression of the fungus.
• Finally, genes isolated from viruses that cause
  hypovirulence in the fungus are being transferred
  into the nucleus of the fungus, expanding the
  effectiveness of this control mechanism.

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HYPOVIRULENCE APPROACH

• There are three viruses that have been identified
  that infect and weaken the chestnut blight
  fungus. Those chestnut trees infected with the
  hypovirulent fungi are able to contain the
  cankers and eventually eliminate the infection.
• In Europe, the European chestnuts were saved when
  the cryphonectria strains became infected by a
  virus and blight fungi were rendered too weak to
  destroy the trees. The infected trees recovered.
• In America, hypovirulent fungi are being studied.
  The results have not been as successful as in
  Europe, since we have too many strains that are
  not compatible and the infection is not able to
  effectively spread. Transgenic manipulation may
  aid in widening the effectiveness of this method
  of control if the infection can be spread during
  sexual reproduction by inserting the virus into
  the nucleus.

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STRATEGIES FOR SAVING THE BUTTERNUT

• USDA Forest Service Project
• The objectives are to
• (a) Establish tree orchards of potentially blight
  resistant trees by grafting the scion wood to
• black walnut root stock. These trees would
  be saved at clone banks for testing and for
  breeding. (b) Investigate the
  dark barked butternut that has been identified
  which appears to be blight resistant. (The
  Slocum butternut tree)
• (c) Investigate those trees that have hybridized
  between the butternut and the Japanese Heart nut
  and
• determine the degree of butternut
  expression. Is back crossing feasible?
  
• Hard Wood Tree Improvement and Regeneration
  Center. Purdue University Forestry Department.
  
• Large collection of pure butternut successions
  (220 trees) and Hybrids (50 trees). They
  collect scion wood and use the grafted stock for
  testing for blight resistance. The center is
  working with the U S Forest Service, North
  Central Experimental Station.
• Southern United States Coalition Project. Similar
  objectives of the Northern group, but trees are
  collected from the southern natural range.

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THE DARK BARK BUTTERNUT
THE SLOCUM BUTTERNUT
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U. S. FOREST SERVICE CLONE BANK PROGRAM
There are 5 clone orchards through out the
mid-west, Iowa, Indiana, Minnesota, Illinois, and
Wisconsin. There are also two gene pool banks,
one in California and and one in Wisconsin.
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THE ROCKLANDBUTTERNUT AND CHESTNUT CLONE
ORCHARD
A LAND OWNER PARTNERSHIP WITH THE U.S. FOREST
SERVICE AND THE AMERICAN CHESTNUT FOUNDATION
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CLOSING THOUGHTS

• The movement of some plants from one continent to
  another has resulted in catastrophic
  consequences.
• Many of the plants have became uncontrollably
  invasive because there are no local environmental
  checks. Examples Buckthorn, garlic mustard,
  honeysuckle, and reed canary grass.
• More catastrophic has been the transmission of
  pathogens from plants that are blight resistant
  to vulnerable plants that have no resistance.
  Examples Emerald ash bore-(ash trees), and
  Cryphonectria - Chestnut tree.
• We cannot change the results of evolution, but we
  can use all of the resources available to control
  these invasive plants and save our vulnerable
  plants.
• IT WILL BE NECESSARY THAT WE LAND OWNERS ASSIST
  IN THIS CHALLENGE.

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