JOURNAL OF AGW01LTURAL RESEARCH 
Vol. XXI Washington, D. C., August 15, 1921 No. 10 
A FUNGUS DISEASE SUPPRESSING EXPRESSION OF AWNS IN 
A WHEAT-SPELT HYBRID 
By Lloyd E. Thatcher 
Assistant Agronomist , Ohio Agricultural Experiment Station 
During the winter of 1919, a number of F 2 hybrids between Triticum 
vulgare Vill. and Triticum spelta L. were grown in the greenhouse of the 
Department of Agronomy of the Ohio Agricultural Experiment Station. 
One bed was planted with 124 grains spaced about 8 inches apart each 
way. The seeds were first treated with the spores of Tilletia foeians 
(B. and C.) Trel., the object of the treatment being to isolate any segre¬ 
gates resistant to the smut that may have come out in the P 2 plants. 
That the treatment was successful is shown by the control. 
An examination of the mature plants showed that they might be 
divided into three classes: Those of which all the grains of all the spikes 
were infected; those of which all the grains of part of the spikes were 
infected; and those of which all the grains of all the spikes were free 
from infection. The number of mature spikes varied from 1 to 6. 
Assuming a simple Mendelian ratio in which AA would represent the 
genotype of the all diseased, Aa the part diseased, and aa the disease- 
free, we would have the following classification: 
Class. 
^ Observed 
number. 
Expected 
number. 
1 
Standard 
deviation. 
Actual 
deviation. 
Ra 
Observed. 
tio. 
Expected. 
All spikes diseased, AA. 
19 
3 1 
4. 82 
12 
O. 613 
I 
Not all spikes diseased, Aa. 
72 
62 
5 - 57 
IO 
2. 322 
2 
Total AA and Aa. 
91 
93 
4. 82 
2 
2 - 935 
3 
All spikes disease-free, aa. 
33 
3 i 
4. 82 
2 
1. 065 
1 
Total AA, Aa, and aa. .. . 
124 
124 
1 
1. 
4. 000 
4 
It is observed that the class of the all diseased spikes is under 
the expectation and the class not all diseased is over the expectation. 
We may assume that the identification is at fault, A A sometimes giving 
Journal of Agricultural Research, 
Washington, D. C. 
yz 
(699) 
Vol. XXI, No. 10 
Aug. t 5■ 1921 
Key No. Ohio-3 
