CHESTNUT BLIGHT AND 
Seguin chestnuts planted in other 
parts of the United States have not 
thrived. 
The Henry chinkapin is a native 
of middle China, ranging from near 
the coast to the far west. In China 
it grows to a height of 75 or 90 feet 
and has a straight, symmetrical 
trunk. In this country the Henry 
chinkapin appears to be more sus- 
ceptible than the Asiatic chestnut 
species to freezing temperatures and 
the blight fungus. 
The blight resistance of chestnut 
species depends upon what type of 
tannin the bark contains and how 
soluble this tannin is. The tannins 
in the Chinese and the Japanese 
chestnut are more soluble than those 
in our native chestnut; it is for this 
reason that these two Asiatic species 
are the more blight resistant. The 
Chinese chestnut is more blight re- 
RESISTANT CHESTNUTS 13 
sistant than the Japanese because its 
tannin is more toxic to the blight 
fungus. 
Owners of Chinese chestnut trees 
should make systematic observa- 
tions on them, to locate the best ones 
for propagation as horticultural 
varieties or for use as parent trees 
for stock to be used in forest, wild- 
life, and ornamental plantings. 
The United States Department of 
Agriculture has distributed more 
than half a million blight-resistant 
Asiatic chestnut trees, for testing, to 
foresters, soil conservationists, wild- 
life technicians, horticulturists, and 
private cooperators. The Depart- 
ment of Agriculture does not now 
distribute blight-resistant chest- 
nuts to the general public. Such 
trees can be obtained from private 
nurseries and from some State 
forest and wildlife agencies. 
BREEDING BLIGHT-RESISTANT CHESTNUTS 
For many years the United States 
Department of Agriculture has been 
crossing the principal chestnut and 
chinkapin species on a large scale, 
in an effort to produce fast growing, 
blight-resistant hybrids to replace 
the American chestnut as a timber 
tree. In general, American chest- 
nut trees that give evidence of hav- 
ing some blight resistance are 
crossed with Asiatic chestnut trees 
that have forest-tree form. Most 
of the first-generation hybrids from 
such crosses are vigorous and up- 
right growing but too susceptible to 
the blight for practical use. Hy- 
brids that show marked resistance 
to infection are used further in the 
breeding work. 
One selection of Chinese chestnut, 
when crossed with American chest- 
nut, produced fast growing, upright 
trees fairly resistant to the blight. 
A number of hybrids of this type 
were produced in 1932, and addi- 
tional ones in 1935 and later, These 
first-generation hybrids resemble 
the American chestnut in such char- 
acteristics as rate of growth, form, 
and leaf shape (fig. 9, D). Their 
blight resistance is less than that of 
the Chinese parent but greater than 
that of the American. For the first 
15 years, the progeny of the cross 
made in 1935 increased in height at 
a rate of almost 214 feet per year, 
and in diameter at a rate of almost 
1% inch per year (fig. 10). When 
these first-generation hybrids are 
backcrossed to the Chinese chest- 
nut parent tree, the progeny 1s 
practically as resistant to the blight 
as the Chinese chestnut and has 
good forest-tree form. These first- 
generation hybrids are being back- 
crossed also to other selections of 
the Chinese chestnut in an effort to 
obtain better forest-tree form and 
a growth rate more like that of the 
American chestnut. ; 
Special attention is being given 
to development of blight-resistant 
