388 
Joumal oj Agricultural Research 
Vol. XXX, No. 4 
in Table I in connection with the pre¬ 
sentation of the data on the relative 
smut resistance of their progeny. 
EXPERIMENTAL DATA 
The first studies on the resistance of 
the progeny of hybrids No. 1015a 1 and 
No. 1015a2 to Ustilago avenae were 
conducted at the Aberdeen Substation, 
Aberdeen, Idaho, in 1919. The seed 
from 49 and 43 F 2 plants, respectively, 
was inoculated and the F 3 plants were 
examined for their behavior toward the 
loose smut. 
In 1920, the seed from individually 
selected F 3 plants was inoculated with 
Ustilago avenae and again grown at 
Aberdeen. The selected plants came 
from rows which showed either a very 
high degree of resistance or of suscep¬ 
tibility in the previous year. 
In 1922, F 4 plants were grown from 
seed harvested from the F 3 rows of the 
1919 sowings. However, no attempt 
was made to grow plants from a single 
F 3 parent. In 1922, also, F 5 plants 
from the F 4 generation of 1920 were 
grown. Separate lots of seed were 
inoculated with Ustilago avenae and 
U. levis. 
The methods employed have been 
fully described in the publications of 
Reed (14) and Reed, Griffiths, and 
Briggs (15). An adequate quantity of 
seed for sowing a rod row was placed 
in a small envelope and sufficient smut 
spores to thoroughly dust the seed 
were added. 
In Table I, the data obtained on the 
reaction of selections from the hybrid 
Fulghum X Swedish Select to Ustilago 
avenae and U. levis are oresented. 
DISCUSSION OF RESULTS 
Reference to Table I shows that 
very great variation exists in the reac¬ 
tion of the different selections to the 
loose and covered smuts of oats. The 
percentage of infection ranges from 
zero to as high as 79 per cent. For the 
purpose of studying the relative resist¬ 
ance or susceptibility of each selection 
as indicated by its reaction to the 
smuts, some method of comparison is 
necessary. Accordingly, on the basis 
of the 1919 results, the following classes 
arbitrarily have been adopted and a 
certain range in percentage of infection 
assigned to each. The classes and 
infection ranges are as follows: 
Per cent 
1. Very resistant- 0 to 5 
2. Moderately resistant-- 5 to 20 
3. Moderately susceptible-- 20 to 40 
4. Very susceptible... 40+ 
On the basis of the data obtained for 
Fulghum and Swedish Select, the 
parents of the hybrids, the former 
would be placed in group 1 and the 
latter in group 2 or 3. 
SMUT INFECTION AT ABERDEEN, IDAHO, 
IN 1919 
As noted in Table I, 92 F 3 families, 
the seed of which had been inoculated 
with Ustilago avenae , were grown. Of 
these families, 25 fall into class 1, 33 
families fall into class 2, and 22 fami¬ 
lies into class 3. The remaining 12 
families proved to be very susceptible 
and fall into class 4. 
The progeny of the 2 Fi plants in 
general has responded in a similar 
fashion. A few more families of hy¬ 
brid No. 1015al are found in the very 
resistant class, while on the other 
hand, the very susceptible class is rep¬ 
resented by an excess of families from 
hybrid No. 1015a2. 
SMUT INFECTION AT ABERDEEN, IDAHO, 
IN 1920 
In 1920, the seed from six different 
individually selected F 3 plants from 
each of several families was inoculated 
and sown. 
Selections were made from two re¬ 
sistant No. 1015al F 3 families (Nos. 
33 and 45), and from five resistant No. 
1015a2 F 3 families (Nos. 9, 31, 37, 38, 
and 54). All of these seven families 
had shown negative results in 1919. 
In 1920, the percentages of infection 
in all the selections from families Nos. 
33 and 45 from No. 1015al, and of Nos. 
9 , 31, and 54 from No. 1015a2, were 
either zero or very small. Two of the 
selections from family No. 37 of No. 
1015a2 showed 8 per cent and 6.1 per 
cent infection, respectively. Two se¬ 
lections from family No. 38 of No. 
1015a2 showed rather high infections, 
namely, 13.4 and 18.7 per cent. With 
these four exceptions, however, all of 
the 42 selections showed a degree of re¬ 
sistance comparable to the F 3 parent 
family. 
Six selections also were grown from 
each of three susceptible F 3 families, 
Nos. 52, 54, and 60, from No. 1015al. 
In 1919, family No. 52 showed 35.2 per 
cent infection. In 1920, the percentages 
of infection of the selections ranged 
from 25.2 per cent to 53.5 per cent. 
Family No. 54 in 1919 had 58.1 per 
cent of infection. In 1920, the selec¬ 
tions showed infections ranging from 
45.7 per cent to 78.5 per cent. Family 
No. 60 in 1919 had 38.2 per cent of in¬ 
fection and, in 1920, the selections 
showed infections ranging from 34.6 
per cent to 45.8 per cent. These se¬ 
lections from very susceptible F 3 fami¬ 
lies showed a wider range of infection 
than the parents. 
