American chestnut

The American chestnut is a big tree.

It grows very fast. It makes many nuts. These nuts are inside a spiny green shell.

Many animals eat the nuts. Bears and deer love them. The nuts help them stay full.

But a sickness came to the trees. It came from trees in Japan. This sickness killed many trees.

Now, scientists want to help. They are trying to make new trees. They want the trees to stay healthy.

The American chestnut is a large, fast-growing tree.

It used to be a very common tree in eastern North America. These trees grow big leaves with saw-like teeth on the edges.

They produce many nuts inside a spiny green shell called a burr.

Many animals like deer and bears eat these nuts for food.

In the early 1900s, a sickness hit the trees. This sickness is called chestnut blight. It is a fungal disease, which is a type of living organism. The blight came from Japanese chestnut trees brought to North America. The disease kills the tree by girdling the trunk. This means it wraps around the tree and stops it from living. It is estimated that billions of trees died from this blight.

Today, scientists are working to help the trees. Some try to cross-breed different types of chestnuts. Other scientists use a gene from wheat to make a new tree. They call this the Darling 58 cultivar. This new tree can fight the acid from the blight. They hope to release these trees into the wild soon.

The American chestnut is a large and fast-growing tree. It belongs to the beech family. This tree is a deciduous hardwood, which means it loses its leaves each year.

You can recognize its leaves by their long and broad shape. The edges of the leaves have large, widely spaced saw-teeth. This trait is why its scientific name is *Castanea dentata*. The word *dentata* is Latin for "toothed."

These trees are important because they produce many edible nuts. The nuts grow inside a spiny, green shell called a burr. Each burr usually holds three nuts lined with tan velvet.

This tree once ruled much of the eastern North American forests. It was a dominant species in the oak-chestnut forest regions. The trees grew well on steep slopes with acidic soil. They were very helpful to the environment and local animals. For example, black bears would eat the nuts to get fat for winter. White-tailed deer and wild turkeys also relied on them for food.

The trees also helped the soil stay healthy. Their leaves contain nitrogen, phosphorus, potassium, and magnesium. When the leaves fall, they return these nutrients to the ground. This helps other plants and tiny living things grow.

Everything changed in the early 20th century due to a sickness. This sickness is called chestnut blight. It is a fungal disease caused by an Asian bark fungus. The fungus arrived when infected Japanese chestnut trees were brought to North America.

The blight was first noticed in 1904 at the New York Zoological Park. A forester named Hermann Merkel saw the disease there. He estimated that 98 percent of the trees in that area were infected by 1906. The disease works by girdling the tree. This means it wraps around the trunk and stops the tree from living. It is estimated that the blight killed between three and four billion trees.

Today, the American chestnut is in a very hard spot. It is listed as endangered in Canada. Most of the original population was lost, leaving only one to ten percent of the original size. Some trees still grow, but they are often just saplings that die before they get old. There are about 600 to 800 large trees in Northern Michigan.

Scientists are working hard to find a way to save the species. One group uses cross-breeding to make trees that can fight the blight. They might cross the American chestnut with the Chinese chestnut. This helps them keep the genes of the American tree while adding resistance.

Other scientists are using a very modern way to help. Researchers at the SUNY College of Environmental Science and Forestry created something called the Darling 58 cultivar. They did this by putting a gene from wheat into the chestnut.

This gene helps the tree make an enzyme. This enzyme breaks down the acid made by the blight. This stops the fungus from hurting the tree's inner trunk. As of 2021, researchers are asking for permission to share these trees with the public. If they are allowed, these would be the first genetically modified forest trees released into the wild in the United States. This work could help the American chestnut return to its home in the forest.

The American chestnut (*Castanea dentata*) is a large, fast-growing deciduous hardwood tree. It belongs to the beech family, known as Fagaceae. This species was once a dominant part of the eastern North American landscape. It thrived in the oak-chestnut forest regions across central and southern ranges. The tree is a prolific producer of edible nuts. These nuts grow inside a spiny, green fruit called a burr. Each burr typically contains three nuts lined with a tan velvet.

Biologically, the American chestnut is a monoecious species. This means it has both male and female flowers on the same tree. It is also usually protandrous, which affects how it reproduces. The male flowers appear as small, pale green catkins. These catkins are about 6 to 8 inches long. The female parts are located near the base of these catkins. They appear in late spring or early summer. Because the species is self-incompatible, it requires two different trees for pollination. This pollination can occur with other members of the *Castanea* genus.

Before the 20th century, this tree played a massive role in forest ecology. It grew best on moist, well-drained, steep slopes with acidic loam soils. In some areas, like Western Maryland, it made up 36% of forested slopes. The tree was a vital food source for many animals. Black bears ate the nuts to gain weight for winter. White-tailed deer, wild turkeys, and the extinct passenger pigeon also relied on them. Even the Greater Chestnut Weevil depended on the tree. The chestnut also improved the soil quality. Its leaves contain high levels of nitrogen, phosphorus, potassium, and magnesium.

A catastrophic event changed the forests forever. In the early 1900s, a fungal disease called chestnut blight arrived. This disease is caused by an Asian bark fungus, *Cryphonectria parasitica*. The fungus was introduced via infected Japanese chestnut trees. These trees were brought to North America in the late 19th century. The blight was first identified in 1904 at the New York Zoological Park. A forester named Hermann Merkel noticed the disease there. By 1906, he estimated that 98% of the trees in that area were infected.

The mechanism of the blight is devastating to the tree. The fungus acts as a vascular disease. It infects the tree and eventually girdles the trunk. Girdling occurs when the disease damages the vascular cambium. This layer is essential for transporting nutrients and water. Once the cambium is destroyed, the tree can no longer survive. It is estimated that the blight killed between three and four billion trees. This caused the population to drop to just 1% to 10% of its original size.

Today, the American chestnut is in a state of functional extinction. While many saplings grow from old root systems, the blight usually kills them before they reach maturity. There are only four mature trees left within its former range. However, some large trees exist outside the historical range. For example, Northern Michigan has between 600 and 800 large trees. In these areas, less virulent strains of the pathogen may be present. The species is currently listed as endangered in Canada under the Species at Risk Act.

Scientists are using several methods to save the species. Some researchers use cross-breeding to create resistance. They may cross the American chestnut with the moderately resistant Chinese chestnut. This process involves backcrossing to retain as many American chestnut genes as possible. Other scientists at the SUNY College of Environmental Science and Forestry use genetic engineering. They created the Darling 58 cultivar by inserting a wheat gene into the tree. This gene produces an oxalate oxidase enzyme. This enzyme breaks down the oxalic acid produced by the blight. This prevents the fungus from destroying the vascular cambium.

The survival of the American chestnut remains a major scientific goal. As of 2021, researchers are seeking government permission to release the Darling 58 cultivar. If approved, these would be the first genetically modified forest trees released into the wild in the United States. This work connects forest pathology, genetics, and conservation biology. It represents a massive effort to restore a lost piece of the North American ecosystem.