Feb. io, 1933 
Genetics of Bunt Resistance in Wheat 
47i 
Table IX.— Frequency distribution of resistance to bunt in a cross between Hybrid 128 
and Marquis, both of which are susceptible when fall-sown 
Variety. 
Hybrid 128. 
Marquis.... 
H X M F 2 . . 
H X M F a . . 
H X M F 4 . .. 
Year 
tested. 
1919... 
63.0 
1920... 
98.1 
1919... 
Not tested. 
1920... 
74 *o 
1920... 
Not tested. 
1919... 
1920. 
Bunt in parent 
row. 
Per cent. 
75 - 9 
76.7 
78.6 
79-4 
80. 9 
81.1 
8!. 3 
83. o 
83.9 
94.3 
96.9 
97.6 
98.4 
Number falling into class with average percentage of 
bunt of— 
5 
15 
25 
35 
45 
55 
65 
75 
85 
95 
2 
1 
3 
1 
3 
I 
0 3 
1 
»i 
! 
5 
53 
276 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
a Seed from a different source, but since Marquis is a variety; recently introduced and appears to be 
constant for all its characters, it is likely that there is no genetic difference in the resistance of these strains, 
for seed from these same strains planted in the spring produced less than 5 per cent of bunt. 
The F 4 generation shows an average of 19.9 per cent less bunt than 
the F 3 parent rows, but this is undoubtedly due to seasonal fluctuations, 
for Hybrid 128 and Marquis showed similar differences in 1919 and 1920. 
A closer study of the F/s indicates that even in these extremely suscep¬ 
tible segregates there is a constant difference in their susceptibility 
comparable to the differences in the susceptibility of the parents. This 
is more clearly brought out by the following figures: 
Average percentage of 
bunt. 
Difference. 
1919 
1920 
From 9 low selections... 
80. 2 
96.8 
16. 6 
62. 2 
72.4 
10. 2 
l 8 . O 
24.4 
6 . 4 
From 4 high selections. 
Difference between high and low. 
Out of the 9 low F 3 rows (between 75 and 84 per cent bunt) 5 produced 
the smallest percentage of the 13 rows in the F 4 generation. Out of the 
4 high F 3 rows (between 94 and 99 per cent bunt) selected, one produced 
the highest amount of bunt in the F 4 generation, and two of the others 
produced more than the average of all the F 4 ’s in 1920. This indicates 
that Marquis carries a weak factor or property for resistance that is 
inherited and is not affected by fall planting. If this be true, strains 
from this cross could be selected that would show a consistent difference 
