June 7 ,1924 A Genetic and Cytological Study of Wheat Hybrids 1019 
The varieties belonging to the vulgare group in all cases have hollow straw 
and the keel on the back of the glume is relatively small. Marquis is an early 
spring wheat and has yellowish glumes, hard, red grain, is considered awnless, 
but has a few apical awns 1 to 10 mm. long. Amby is an Australian wheat 
which is completely awnless and has white glumes and white kernels. Washington 
Hybrid 143 is a club wheat with very soft grain and apical awns 2 to 10 mm. long. 
Crosses were made between Marquis X Kubanka, Hybrid 143 X Alaska, 
Marquis X Alaska, Hybrid 143 X Polish and Amby X Kubanka. The F 2 gen¬ 
eration of each cross was grown at the Washington Agricultural Experiment Station, 
Pullman, Wash, in 1921. Conditions in eastern Washington are ideal for growing 
wheat for genetic studies, because the semiarid climate permits maturity without 
any discoloration of glumes or awns and the color characters can be studied 
readily. The percentage of segregates which will germinate and mature is also 
much higher than is the case in the Middle Western or Eastern States. Data on 
height, time of maturity, and per cent of sterility of the Fj plants were obtained at 
the Washington Experiment Station. One head from each F 2 and F 3 plant was 
sent to the Maine Agricultural Station for a more detailed classification. A code 
was made for most characters, and all data were punched on cards so that the 
material could be analyzed with the aid of a sorting machine. * I. 2 3 
In certain crosses each character was correlated with every other character 
to determine the degree of association between the different characters. The 
-correlation ratio, the correlation coefficient, and the coefficient of contingency 
were used, depending on the nature of the data. In obtaining correlations be¬ 
tween F 2 and F 3 the mean values of the F 3 families were used in most cases. 
Certain of the intermediate types in F 3 were selected and grown for a cytological 
study in F 4 . 
STERILITY IN SPECIES CROSSES 
The degree of sterility in each of the five crosses is shown for the different 
generations. In the Fi of each cross the actual number of grains per spikelet was 
used, but in F 2 and F 3 only the grains in the two outer florets were considered, 
so that two grains per spikelet would be complete fertility. In the parent varieties 
the grains per spikelet ranged from about 1.7 to 2. 
* The following code was used in describing Fi and F 3 segregates: 
A. Type of culm— 
1. Hollow. 
2. Intermediate. 
3. Solid. 
B. Diameter of culm in millimeters. 
•C. Type of spike— 
1. Open. 
2. Intermediate. 
3. Compressed. 
D. Type of glume— 
1. Slightly keeled. 
2. Medium keeled. 
3. Strongly keeled. 
E. Shape of glume— 
1 . Square. 
2. Medium. 
3. Pointed. 
F. Color of glume— 
1. Yellow. 
2. Brown. 
3. Black. 
G. Outer glume pubescence— 
1. Absent 
2. Slight. 
3. Heavy. 
H. Awned. Ranging from absent to those more 
than 10 cm. long. In F 3 the actual length of 
the longest awn was recorded. 
I. Awn color— 
1. Yellow. 
2. Brown. 
3. Black. 
J. Length of rachis in centimeters. 
K. Texture of rachis— 
0. Strong. 
1. Intermediate. 
2. Brittle. 
L. Number of spikelets. 
M. Number of grains. 
M. Number of grains per spikelet. 
N. Grain length in millimeters. 
O. Grain shape. 
P. Grain color, ultimately classified as either white 
or red. 
Q. Grain texture, starchy, intermediate, and very 
hard. 
i T. Type of head. Segregates were classed according 
I to their resemblance to the different species 
I of wheat, vulgare, durum, spelta, etc. 
