Feb. io, 1923 
473 
Genetics of Bunt Resistance in Wheat 
wheat. The particular phase treated is the development of a commer¬ 
cially desirable wheat which will not develop bunted heads even on a 
badly infected soil. Emphasis has been placed on inheritance of bunt 
resistance, but the ultimate practical application of the principles in¬ 
volved has been continually kept in mind. (PI. 3, B.) 
The first tests for resistance were made in 1914 when a few of the 
common commercial varieties were tested for comparative resistance 
under conditions favoring maximum infection. During the next two 
years, while these and other varieties were being tested in greater detail, 
methods of infecting the seed, recording the data, and computing the 
resistance on a comparative quantitative basis were developed and stand¬ 
ardized. In an endeavor to obtain the best possible material for the 
breeding work, more than 500 named varieties, from the principal wheat 
districts of the world, including representatives from the eight species, 
have been tested for resistance. 
Most of the varieties tested proved to be either very susceptible or lack¬ 
ing in winter hardiness. Thus the representatives of the four species, 
einkorn, polish, spelt, and emmer, although all very resistant, were dis¬ 
carded because they were of no commercial value, either from the stand¬ 
point of yield or hardiness. One poulard (Alaska) was used as the male 
parent in several crosses, mainly because of its bunt-resisting qualities. 
One club (Hybrid 128) was selected for two of the crosses described below 
because of its stiff straw, early maturity, and prolificacy, notwithstanding 
its malignant susceptibility to bunt. The other six varieties were selected 
for the breeding work from the vulgare group because they were common 
commercial varieties (with the exception of Florence, which was selected 
for its exceptional resistance) in the Northwest, and contained the 
greatest range of desirable characteristics. 
Alaska, Hybrid 128, Turkey, Fortyfold, Red Russian, and Jones’ Winter 
Fife have the winter habit of growth; that is, they will not head out if 
planted in the spring, and are considered sufficiently winter hardy for fall 
sowing. This is of prime importance because the chief losses due to bunt 
occur in winter wheat. Marquis and Florence are spring wheats and are 
not considered sufficiently hardy for fall sowing, but were such good milling 
wheats and so resistant to bunt that they were used for the additional pur¬ 
pose of studying the inheritance of winter hardiness. 
These eight varieties (PI. 2, B; 3, A) have been grown as pure lines from 
individual plant selections for 6 to 15 years and from the first have bred 
true for their morphological characters and may be assumed to be con¬ 
stant, within the limits of soil and seasonal fluctuations, in their compara¬ 
tive resistance to bunt. 
Turkey is one of the most resistant of all the wheats tested, seldom 
producing above 5 per cent of bunted heads, even under the most favora¬ 
ble conditions for infection. From one-fourth to one-half of the plants 
may show infection, but only a few flowers, or at most only part of the 
heads on an infected plant produce smut balls, the remainder producing 
normal wheat. The other resistant varieties, Alaska, Florence, and Mar¬ 
quis, show similar characteristics in that only a small part of the flowers 
on the infected plants are destroyed by the fungus. The two very sus¬ 
ceptible varieties, Hybird 128 and Winter Fife, on the other hand, do not 
normally produce anything but smut balls on the infected plants, the 
number of flowers or heads escaping being negligible compared with those 
that are destroyed. An occasional plant escapes infection altogether and 
produces normal grain; but once the parasite establishes itself within the 
