“Fast-forward 30-plus years of breeding work,
and what we see is, blight resistance is much
more complicated than we really thought,” says
Tom Saielli, a forest scientist for the foundation.
Scientists now believe that as many as nine
gene regions working together may be responsi-
ble for providing blight resistance, which makes
breeding a challenge. The real question is, What
is the right combination of genes to produce
blight resistance? Breeding also requires many
new generations to make progress, and each
generation takes years.
Genetic engineering offers a controversial
shortcut to creating a truly American blight-
resistant chestnut. In the 1990s Charles May-
nard and Bill Powell at the SUNY College offungal spores enter the trunk, where they release
oxalic acid that kills tree tissue.
As a species, American chestnuts have sur-
vived by shooting up clones from the roots of
dead trees. But it’s a Sisyphean task; blight is
inevitable with age, and a tree’s ability to clone
itself is not infinite.
In their attempts to save the chestnuts, for-
esters have sprayed the trees with fungicides,
infected them with fungus-killing viruses, and
even burned infected trees to the ground. Efforts
to breed American chestnuts with Chinese coun-
terparts to create a hybrid resistant to the blight
began as early as the 1930s and in earnest in
the 1950s. The American Chestnut Foundation
began formal work on the hybrid in the 1980s.
136 NATIONAL GEOGRAPHIC