American Chestnut Tree Project

The Southbury Land Trust has planted several experimental back-cross hybrid American chestnut trees as part of the groundwork for future restoration efforts to bring this stately tree back to the forests of eastern North America. These trees are being evaluated for resistance to the chestnut blight fungus which decimated the American chestnut from about 1904 to the 1940s.  The chestnut blight fungus was introduced to the U.S. from Asia accidentally on live Chinese or Japanese chestnut trees, which were and still are widely planted as nut or yard shade trees.

Prior to the American chestnut blight, the American chestnut was one of the most prevalent and dominant trees in the forests of the eastern U.S., and provided an extremely important food source for wildlife as well as humans. More reliable than oaks as a food source for wildlife, chestnuts produced a good nut crop nearly every year, as opposed to the intermittent oaks which had good nut crop years followed by bad. Even names of Southbury Land Trust properties such as “Chestnut Station”, and “Chestnut Tree Hill Estates” show historical importance of the American chestnut in our area.

The Connecticut Agricultural Experiment Station and The American Chestnut Foundation are conducting valuable research to create, through back-cross hybridization, a viable American chestnut tree; one which is resistant to the chestnut blight and can successfully compete with other forest trees for survival and vigor, as well as be indistinguishable from a pure American chestnut. After years of research, the two organizations are getting closer to their goal.

Back-cross Hybrid efforts are as follows:

  • Japanese and Chinese chestnut trees have resistance to chestnut blight, but they are grown as an orchard type tree in full sunlight and don’t thrive in dense forest. Additionally, they do not grow dramatically tall as the American chestnut once did.
  • All chestnut tree species can be hybridized (crossed with other chestnut species). A large number of small trees still exist as “shoots” in the woods because the root system of the chestnut tree is resistant to the fungal infection. Occassionally a “shoot” survives long enough to produce nuts before the tree is killed by the blight. These are trees that the chestnut researchers worked with.
  • When an American chestnut is crossed with a Chinese or Japanese chestnut, the offspring may have resistance to the chestnut blight, but do not have the potential to grow as tall the American chestnut or have the exact same leaf form.
  • These hybrids that are blight-resistant are then crossed back against a pure American chestnut, creating offspring that are genetically 75% American chestnut.
  • Then these offspring that are blight-resistant are crossed back against a pure American chestnut, creating offspring that are 87.5% American chestnut.
  • Then these offspring are crossed back against a pure American chestnut, creating offspring which are 93.75% American chestnut in appearance, stature and vigor yet still contain the blight-resistance from their Asian great great grandparents!

 

For more information and how you can help:

Join The American Chestnut Foundation:  acf.org

Check out articles on American chestnut programs with the Connecticut Agricultural Experiment Station:   ct.gov/caes