Tree ID - DNA Analysis

Chestnut Identification

Leaves to be examined should be fully expanded, from parts of the tree exposed to full sun and not from within 15 cm of flowers.

Castanea dentate (American chestnut)

Before chestnut blight reached the Carolinian forests this was a tree 18-24 m (occasional 30 m) tall. Now mature trees are uncommon within the native range and usually found as a shrubby cluster of sprouts or as a slender, understory tree up to 18 m tall. The twigs are smooth, reddish to chestnut brown in colour; the buds are smooth and brown and asymmetrically bullet-shaped, usually askew on the twig. Leaves are hairless or with only a few short hairs on the mid-vein of the lower surface, oblong, pointed at the tip, and acute at the base where they join the petioles with coarsely toothed margins with a hook. Mature leaves are light green and paper-thin, and droop down from the twigs. Burs are at the end of the branch with up to 3 nuts per bur.

Castanea mollissima (Chinese chestnut)

Chinese chestnut trees range in resistance to chestnut blight from very susceptible (as susceptible as American chestnut trees) to very resistant. Many cultivars are very cold tolerant. They can usually be recognized by their more oval shape, thick leathery, coarsely serrated leaves that are densely or sparsely hairy on the lower surface. Twigs are greenish-brown to buff-yellow and downy. Buds are hairy, tan, dull brown to black, rounded and flat against the stem. Burs contain 2-3 nuts, with nut size of 1.87 cm to 5 cm, are rounded with a hairy tip, a sunburst pattern is uncommon.

Castanea crenata (Japanese chestnut)

Japanese chestnuts are usually very resistant to chestnut blight and ink disease, and some cultivars have been selected for their resistance to Oriental Chestnut Gall Wasp. The leaves are often dark, shiny green on top and the sides of the leaves are somewhat parallel. They have dense or sparse hairs on the lower surface with many glands. Leaf margins usually have bristle-like projections instead of deeply cut teeth. Twigs are delicate, dark reddish-brown and downy and become smooth as they mature. Buds are glossy, brown and round in shape. The nuts are medium to large (2.5 to 5 cm), 2-3 nuts per bur and the pell covering the nut inside the shell is hard to remove and often bitter when the nuts are fresh.

Castanea sativa (European chestnut)

Trees are tall and straight like American chestnut trees. Leaves are usually straight across where they join the petiole, and have long hairs on the veins of both the lower and upper surface. They usually stand out nearly straight from the twigs. The teeth tend to be triangular, big, sharp or rounded with no hook. Twigs are thick, coarse, brown and are downy at first and become smooth with maturity. Nuts are about the size of American chestnut, 2-3 per bur.

Think You Have an American chestnut – Want to Check it’s Pedigree?

The Canadian Chestnut Council has made arrangements with Dr. Brian Husband at the University of Guelph to extract, sequence, and analyze the DNA from submitted leaf samples. To recover the cost of lab materials and sequencing, a fee of $25 per sample will be charged. If you have a sample that you want to check, please contact Heather Dover by filling out the form below. She will advise where the sample can be sent or make arrangements for it to be picked up.

American chestnut - DNA Sampling Procedure - Simplified

1. Select an appropriate leaf.

Sample a fresh, mature leaf only, preferably not from a branch with blight. Do not sample leaves that are withered, yellowing, diseased, or insect-damaged. A leaf that is in good health, fully intact, and recently completed opening is the best candidate for sampling for DNA testing. Only one leaf per tree is required for DNA testing, but if the leaves are of lower quality, 2 or maybe 3 can be sampled.

2. Prepare The Envelope

Use a paper envelope that will fit in the envelope that you will use to submit the sample/samples (a brown coin envelope or equivalent is a good choice). Label the sample envelope with an ID for the tree and include in the envelope a completed “Reporting a Chestnut in the Wild Form” that can be found on the Canadian Chestnut Council’s website under the “Found a Chestnut/Report a Chestnut” link. Please be sure to include the date taken and the contact information of the person submitting the sample/samples (name, address, email, and phone number). If multiple samples come from the same tree, be sure to mark this clearly on the envelopes.

3. Take the sample.

Using a clean pruner (sterilized is best, see below), carefully remove the selected leaf from the tree. It is fine to cut the stem of the leaf or even to cut off a small portion of the leaf closest to the branch, as long as the sample leaf is mostly intact. If you are sampling multiple Chestnut trees with the same pruner, you should sterilize the pruner between trees by washing it with a diluted alcohol or bleach solution. This helps to prevent any chance of chestnut blight being spread from tree to tree. CAUTION: Chestnut blight is a wound pathogen, which means it infects trees through cuts and scrapes in the tree’s bark. Take extra care not to scrape or damage the tree’s trunk or branches when taking a sample!

4. Prepare the sample for submission

Place the sampled leaf in the prepared envelope (if multiple leaves were sampled from the same tree, put each leaf in a separate sample envelope). It is okay to fold the leaf neatly, if that is needed to fit the leaf inside of an envelope, but try to limit the amount of folding of each leaf. Folding once is fine, but more than that will affect the drying process, not allowing them to dry out properly, as will balling up or scrunching up the leaf. Multiple leaves in the same envelope will also hinder drying. If you have some, immediately add 20-25 ml (e.g., 2 tablespoons) of silica gel into the paper envelope with the leaf sample. Do not seal the envelopes. Leaving them open helps with air circulation and allows for checking the samples and changing out the silica. If you do not have silica, it will be put in when the samples are received.

5. Submit the Sample/Samples

Contact Heather Dover by filling out the form below for information as to where to send your sample. Multiple sample envelopes can be submitted in the same envelope/package. Dr. Brian Husband’s lab will look after the drying and preparation of the samples for DNA extraction.

THANK YOU for your interest in the Preservation and Restoration of the American chestnut.

Contact Heather Dover