Death and resurrection of the perfect tree

Mort et résurrection de l’arbre parfait

Photo: Wikimedia CC
Chestnut, american Castanea dentata”), illustration from d'”History of the forest trees of north America”, by François André Michaux

Since always, they serve to build as much as dream… In this summer series, The Duty attempts to identify what wood they are made out of trees that surround us. Today : the chestnut tree (american).

The interview is almost over. Christie Lovat speaking for a good hour of the American chestnut for which she has recently devoted her doctoral thesis in plant sciences at McGill University.

She leaves a bench of the courtyard to the rear of his house of Saint-Lazare near Montreal. She invites them to follow her in her pretty garden, where she discover a protected, three young tall trees of a few feet, difficult for the moment to distinguish it from the rest of the abundant vegetation.

She gently lifts a small branch, and its long leaves of a tender green. “It is an offspring that comes from my research, a tree of the laboratory, one of my babies in test tubes,” she said, laughing.

The formula is even more a fly that Mrs Lovat is pregnant with her first child. She has bought the house of his mother, where she grew up. Large trees of several species along the surrounding streets. There is even a growing Chestnut close.

“I have always enjoyed the ecology, the plants,” said the biologist explaining how he heard for the first time the American chestnut in a course in the bachelor’s degree. The guest speaker of the day was mentioned in passing a slide that this tree was once the most common of the east coast of the United States and that its loss was the greatest ecological disaster in american history.

“The speaker is switched to the next slide,” said the former student. We were all amazed in the class. My mind has overheated. “

The lesson is more than ever. “I was always surprised how people can forget a species as soon as it disappears. We often speak of this issue at the university because we lose and we will lose many species in the coming years. It would be a tragedy if the tiger was no more. But it will take how many generations before no one will remember this exceptional animal ? “asks Mrs. Lovat.

The perfect tree

The American chestnut appears to him-even non-standard, king, sylvester, ” the perfect tree “, summarizes Mrs. Lovat, listing its outstanding features. Castanea dentata grows very straight and very quickly to reach a height of 30 to 45 meters, as the highest of the large maple trees, with a trunk diameter of 3 metres. It gives a hard wood and clear favourite of cabinetmakers and carpenters.

Its sweet fruits, in groups of three, will fall in the autumn of their bugs thorny. A tree produces 6000 approximately per season, year after year. The chestnuts have long nurtured the wildlife of the woods, from squirrels to bears.

They engraissaient also the cattle and filled the human. The ancestors were gathering these wonders of nature as it still goes to apples. Winslow Homer was engraved a scene of chestnutting, verb coined to describe the collection that no longer happens. “Chestnuts roasting on an open fire “, sang Nat King Cole in The Christmas Song, written after the Second world War, when that is completed the disappearance of the tree, its fruit, a whole world of natural and cultural in fact.

“When a plant of this size dies, it is a part of the culture is going,” said the researcher. Try to imagine Canada without the maple tree, the Québec without the maple syrup. “

The canker of the bark

Castanea dentata, tree said campaign, was widely spread in the forests of the eastern United States and southeastern Canada. We planted little towns. Us maps of its former range, made just before the catastrophic disease outbreak, cover a very large area diagonally from the Mississippi to Maine, to the southern part of Ontario, bordering on the quebec border.

Mrs. Lovat believed that deciduous trees were growing here also, since it is still, up to La Tuque. She reminds us that there are New Brunswick and Nova Scotia, the oldest having been planted by loyalists after the revolution of 1776.

The readings today are about 1500 chestnut american mature in Canada, adulated by conservation organisations bringing together “chestnutters ” who give them names. The tree is registered on the federal list of endangered species since the 1980s.

This people leafy had approximately 4 billion people at the end of the Nineteenth century, composing one-quarter of the forest appalachienne. A fungal disease native to Asia, introduced by wave with the mode of the exotic plants, only took a few decades to destroy it all, galloping a hundred miles per year, starting in the 1910s in the State of New York.

The chestnut trees, chinese or japanese are resistant to the fungal pathogen agent of canker of the bark. Their american cousins die of the ” burning east “, in a year, with a fatality rate in excess of 99 %. The new shoots do not stand up as soon as they reach a modest height.

A genetic modification

The renaissance of the treasury new year’s eve has always relied on crosses with trees from asia. “The two chestnut trees are very different from several points of view,” says Ms. Lovat. Trees in china are smaller, its fruits are more bitter. This poses the fundamental problem of how much DNA of a chestnut can be implanted in another without altering the host basically. “

His own experiences as doctoral have rather rationally bet on the improvement of a technique of genetic modification of trees to make them resistant to invasive species, Cryphonectria parasitica. Genes of barley have been used with success in the United States, where the new specimens appear more resistant to the pathogen than the chestnut asian.

Only, the process us is random, with a success rate hovering around 1 %. The quebec researcher has been able to multiply the chestnut samples. The approximately 40 plants in his garden come from one of its successful tests, hundreds of others are already being planted everywhere. The phd has been defended in the spring of 2019.

The discoveries of Christie Lovat will be able to assist the efforts of regeneration of both sides of the border. The canadian Council of the chestnut tree lists for years, the surviving trees and developing programs of cross-pollination to produce offspring redisséminés. The projects include planting in northern Ontario and Quebec.

“For the first time, I’m pretty optimistic to say that it is completely feasible to see in my lifetime a new forest of chestnut trees, with the americans,” said the expert in conclusion. It cites two barriers to this utopia feasible : the fund and is a matter of substance.

“We have never approved the release of a living genetically modified to replace another which is natural. He is not here to improve a plant edible for agriculture. The goal is to save a species in danger of extinction by using genetic transformation. This effort requires a change of paradigm. “

She even admits to having long thought evil of any genetic manipulation. The in-depth study of the genes has changed his opinion.

“Genes are not static,” she says, closing the interview, before the visit of her garden with her babies in the laboratory. “The human genome has tens of genes derived from the virus. The Homo sapiens are DNA neanderthal. I have to agree, so now the idea of saving the American chestnut with genes from another species. “

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