Once this tree produced nuts, Dunstan crossed the grafted tree to a Chinese chestnut
and let it grow to production.
Sadly, at the dawn of the 20th century, a fungus introduced on imported Chinese chestnut
trees very nearly caused the extinction of the American chestnut, or Castanea dentata.
About eight volunteers planted the chestnuts from blight-resistant American chestnuts that were produced from crossing them with Chinese chestnuts
, which are naturally resistant to the fungus.
He expects that this will allow researchers to produce a chestnut that is pure American except for the addition of a few genes from the Chinese chestnut
that confer disease-resistance.
The saplings used in this planting are products of 25 years of genetic back crossing with the Chinese chestnut
Upper grades study forest ecology, perform DNA experiments, and study the genetics of backcrossing Chinese chestnut
hybrids to surviving native chestnuts, aiming for a tree that incorporates the desirable characteristics of the native with just enough Chinese to resist blight.
The somewhat inferior European and Chinese Chestnut
have proven to be resistant to the fungus and some success has been made in grafting them to American Chestnut rootstock.
The five American chestnut seedlings planted at the field headquarters of the Massachusetts Division of Fisheries and Wildlife in Westboro originated from a seed that was a cross-breed between the American chestnut and the disease-resilient Chinese chestnut
Today, TACF's research farms encompass nearly 160 acres and more than 60,000 American and Chinese chestnut
trees which are part of its national breeding program.
Researchers have been cross-breeding the American chestnut with the Chinese chestnut
, which is resistant to the blight.
Founding The American Chestnut Foundation, their goal was to develop a seed or nut that would produce a healthy chestnut tree with fully American chestnut characteristics, but for one thing: Built into the chestnut's genetic makeup would be the blight resistance that allowed its cousin, the Chinese chestnut
, to thrive throughout Asia, where the blight fungus originated.
Through careful cross-breeding with blight-resistant Chinese chestnut
trees, the Foundation hopes to create a blight-resistant offspring that is 94 percent American.
In 1983, the American Chestnut Foundation began a more scientific approach: they embarked on the long genetic journey of breeding a hybrid that would have the blight resistance of the Chinese chestnut
and the phenotype, or appearance, of the stately American chestnut.
Prominent among the non-native species are many edible fruit and nut species including common apple (Malus domestica), Chinese chestnut
(Castanea mollissima), European or sweet chestnut (Castanea sativa), ginkgo (Ginkgo biloba), European plum (Prunus domestica), and European pear (Pyrus communis).
Chestnut Hill Tree Farm specializes in growing Dunstan hybrid chestnuts, a blight-resistant variety that is a cross between a disease-resistant American chestnut discovered in the 1950s and three Chinese chestnut