30 
Vol. XXIX, Nc. I 
Journal of Agricultural Research 
77 per cent at St. Paul and 68 per cent 
at Mandan. The F_> hybrids showed 
from 5 to 95 per cent of infection at 
both points, averaging 45 per cent at 
St. Paul and 46 per cent at Mandan. 
There was no distinct separation be¬ 
tween resistant and susceptible strains. 
Additional material was studied for 
resistance, upon which individual rust 
notes were recorded only on plants 
about as resistant as the Kota parent or 
having an estimated infection of 15 per 
cent or less. This was thought to be 
about the maximum amount of infec¬ 
tion which could occur without dam¬ 
age. By taking this estimated infec¬ 
tion of 15 per cent or less as resistant 
and grouping the remainder as suscep¬ 
tible at both St. Paul and Mandan, F 2 
results were found to agree very closely 
to a 2-factor hypothesis. The data 
obtained are shown in Table XX. 
Table XX shows that, on 
the arbitrary division made, 
there is slight evidence of ma¬ 
ternal influence. Where the 
susceptible Hard Federation 
was used as the female parent, 
a close fit to the 15:1 ratio was 
obtained in both cases. Where 
the resistant Kota was used as 
the female parent a greater 
proportion of resistant plants 
was obtained and at St. Paul 
the deviation from the ex¬ 
pected ratio was greater than 
three times the probable error. 
The grand average for both 
crosses at both stations, how¬ 
ever, shows that a very close 
fit was obtained in F 2 for the 
assumption that two Men- 
delian factors are involved 
for stem-rust resistance in this 
cross. 
At Mandan, N. Dak., in 
1923, the 724 F 3 plants, 
which were labeled for date 
of heading and measured for 
height, were examined indi¬ 
vidually and the infection of 
stem rust estimated. The data, 
obtained are given in Table 
XXI and shown graphically 
in Figure 6. 
Fig. 6.—Frequency distribution, by percentage of stem-rust 
infection, of F 3 selections and of the Kota and Hard Fed¬ 
eration parents at Mandan, N. Dak., in 1923 
Table KXI.— Stem-rust infection on 724 Fs plants of the Kota-Hard Federation- 
and reciprocal crosses, and comparison with the parents, grown at Mandan , 
N. Dak., xn 1923 
Frequency classes in percentage of stem- 
rust 
F 3 hybrid 
Hard Federation 
Kota 
Number 
Percent¬ 
age 
Number 
Percent¬ 
age 
Number 
Percent¬ 
age 
5 .. 
68 
i 
9.4 
49 
65.5 
15___ __ 
326 
45.0 
26 
34.7 
25 . ... 
175 
24.2 
35______ 
71 
9.8 
45. . .. 
33 
4.6 
55______ 
27 
3. 7 
! 
65_ _ __ 
16 
2.2 
1 
1. 1 
75 _ . _ 
5 
0.7 
22 
23. 2 
85. .. .. 
3 
0.4 
58 
61.1 
95_ ___ 
14 
14.7 
Total...... 
724 
100.0 
95 
100.1 
75 
100.0 
