Chestnut is estimated to be familiar to most people, this is one of the more common crops in our country, it has a very iconic prickly fruit, which brings some trouble to hungry children, but the nuts inside are very fat, and the taste after cooking is also very good, which is loved by people.
In our country, chestnut trees may have been planted for more than 2,500 years, so it is found in many ancient books, but the chestnut trees we plant now will be different from those planted before.
Pictured: Chestnut trees today
Today's chestnut trees are often relatively low, very efficient cultivated species, but in fact, wild chestnuts or chestnut trees that were first planted by us are very tall trees, often one of the tallest and largest tree species in the forest.
My grandfather planted a chestnut tree in the last century, this tree is still there, it is estimated that it must be at least 30 meters high, the trunk is almost as thick as two children hugging, but I don't know if it is older, or the essence is like that, this boss chestnut tree is often empty after fruiting.
A huge ancient chestnut tree in Ma'anshan, source: The Paper
Chestnut is a species of beech family, which is widely distributed worldwide and plays one of the most important ecological roles in many regions.
For example, the North American chestnut tree, the American chestnut tree (Castanea dentata), with its tall stature and ultra-fast growth rate, dominates most of the eastern forests of the United States, in Pennsylvania, it is estimated to account for 25-30% of all hardwoods, and in the Appalachian Mountains 25% of trees are chestnut trees, the most conservative statistics alone in the United States may have 4 billion.
Pictured: Chestnut trees cut down during American colonization, and these trees are the tallest trees in their forests
Because chestnut is resistant to rot, straight grain, and suitable for furniture, fences, and building materials, in colonial times, chestnut was the first choice for wooden house foundations, fence posts, floors, and coffins.
Later, railroad ties in the United States, as well as telephone lines and telephone poles, were made of chestnut wood, and many are still in use today.
Pictured: American painting depicting stepping on a chestnut
Similarly, thanks to its large numbers, its nuts feed billions of animals — from insects to birds and mammals, and there have even been cases in the United States where pigs, cattle and other livestock were herded in forests dominated by chestnut trees.
Chestnut trees were also often reported in 19th-century newspapers, such as train cars full of chestnuts, sold fresh or baked in big cities.
©Peatcher
However, with the pace of globalization, creatures around the world have also taken advantage of the wind of global trade to frantically develop a wave of territory, and species invasion is one of the most obvious side effects of globalization, and no country or region is immune.
At the beginning of the 20th century, a deadly fungus from Asia, Cryphonectria parasitica, was introduced to the United States, causing the near extinction of chestnut trees that had long been mixed in the United States.
There are two theories about how fungi came to the United States:
Pictured: Chestnut blight
One is that around 1904, the United States introduced Japanese chestnut trees for commercial purposes, and this chestnut tree carried chestnut blight bacteria; The other is when importing Japanese chestnuts, I accidentally "imported" fungi as well.
But the theory of how the fungus was found is largely consistent, it was first discovered on a chestnut tree at the New York Zoo, who discovered and reported the lesion, and by 1905 the fungus was isolated and described by the American mycologist William Murrill.
Chestnut blight infection is now called chestnut blight, Asian chestnut trees and this fungus co-evolved, natural resistance to this fungus, but the United States does not, the American chestnut trees infected by it will basically die, and are very susceptible.
Figure: The initial stage of infection
When chestnut trees are infected, initially the fungus leaves orange "ulcers" on the branches and trunk, as well as obvious dents, somewhat similar to bruises on a person, which hinder the tree's loss of water and nutrients.
Chestnut blight is not only infected by chestnut trees in the United States, but also many trees - such as oak, red maple, antler paint and so on.
But for other tree infections only those "ulcers" that stay on the surface, trees will be affected, but death is not common, only chestnut trees die easily.
Until the tree dies, the fungus stays on the tree, producing spores and spreading through the wind.
Over time, infected trees, whose bark will gradually age, eventually crack and allow spores to enter the trunk, where the fungus releases oxalic acid that kills the tree tissue, eventually causing the entire trunk to die.
The good news is that chestnut blight bacteria do not grow well in soil, so the roots of chestnut trees can survive in many cases, and chestnut trees can germinate and grow again through their roots.
But the bad news is that when it comes out of the soil, it will be infected again.
However, for young trees, their bark is relatively active and not easily aged, so it is more difficult for fungi to kill them, but it is difficult to survive over time, few chestnut trees live to sexual maturity, and most importantly, the germination of roots is not infinite.
Pictured: Here is a wild American chestnut tree seedling, can you find it?
So, only 50 years have passed since the discovery of this fungus - around 1950, 4 billion American chestnut trees have almost disappeared, labeled functionally extinct, adult trees are almost impossible to find, and most of what remains are seedlings that have just developed from their trunks.
Chestnut blight is arguably the most devastating and economically costly invasion in the history of species invasions on Earth, and it has led to the fact that the United States has not sold new chestnut wood for decades in recent decades, and they still consume about 100 tons of chestnut a year, most of it through imports.
In fact, such a thing is quite scary to think about, a sudden fungus, directly led to the almost extinction of another species that has an absolute advantage in its place of origin.
Such things may often occur in the history of the earth, such as the extinction of dinosaurs, and some scholars believe that it may be related to the emergence of viruses or other pathogenic bacteria.
But now there's good news: after decades of hard work, scientists have found a way to help American chestnut trees — genetic engineering.
In wheat, there is a gene that produces oxalate oxidase, which breaks down oxalic acid produced by wilt fungi and then spares the host.
Pictured: Darling 58 in a greenhouse
In 2014, the work was successful when scientists successfully transferred wheat's disease-resistant genes to American chestnut and named the new American chestnut, Darling 58, with the study's engineer, Herb Darling.
The new disease-resistant chestnut tree may be able to replay the ecological role of the former American chestnut tree and save the American ecology, but whether things will really develop as expected, no one can say.
Therefore, people are still cautious about Darling 58, this new species (let's call it a new species) is still restricted from cultivation, only in specific areas, not released into the wild.
Resources:
1.https://www.nationalgeographic.com/environment/article/genetically-modified-american-chestnut-trees-conservation
2.https://acf.org/the-american-chestnut/history-american-chestnut/