18 
Journal of Agricultural Research 
Vol. XXIX, No. I 
Table XII .—Segregation of 5,737 F 3 plants of the Kota-Hard Federation and 
reciprocal cross into two classes for color of kernel, when grown at Davis, Calif., 
in 1923 
Davis, Calif. 
F 2 families 
F 3 plants 
Fj classes and segregation in 
the F 3 
Per¬ 
centage 
of class 
Per¬ 
centage 
of F 2 
Kernels 
Devia¬ 
tion 
Prob¬ 
able 
error 
Num¬ 
bers 
Red 
White 
from 
ratio 
indi¬ 
cated 
Kernels white: 
Whit * 1 
80 
100.0 
6.0 
2,495 
Total_ 
80 
100.0 
6.0 
2, 495 
Kernels red: 
Fed 
55 
47. 0 
44.2 
1,501 
821 
Red and white— 
3:1 ratio___ 
37 
31.6 
29.7 
254 
15 
9. 59 
15:1 ratio_ 
25 
21.4 
20.1 
623 
43 
1 
4.21 
Total_ 
117 
100.0 
94.0 
2,945 
297 
.. 
— 
197 
200.0 
100.0 
2,945 
2, 792 
The data show that the white- 
kerneled strains bred true to that 
color. The red-kerneled strains bred 
true or segregated into red and white in 
either the 3:1 or 15:1 ratios. From 
the 37 F 2 families which segregated 
according to the 3:1 ratio there were 
821 red-kerneled plants to 254 white in 
F 3 , a deviation from the expected of 
15 =t 9.59. Of the 666 F 3 plants which 
segregated according to the 15:1 ratio 
the deviation from expected was 
1± 4.02, which indicates an unusually 
close fit. 
Of the F 2 red-kerneled strains, seven- 
fifteenths, or 46.7 per cent, should have 
bred true and four-fifteenths, or 26.7 
per cent, should have segregated in 
both the 3:1 and the 15:1 ratios. As 
shown in Table XII, the percentages 
obtained were very close to the expected. 
DATE OF HEADING 
Earliness often is an important eco¬ 
nomic factor in successful spring-wheat 
production in the dry sections of the 
United States. The date of heading is 
thought by the writer to be the best 
note to use in a study of earliness under 
drought and rust conditions. It is 
more reliable and shows a greater 
range of variation than the date of 
ripening where adverse environmental 
conditions affect the wheat crop near 
maturity. 
Farrer (11) found earliness in wheat 
hybrids to be intermediate between the 
parents and that there was no differ¬ 
ence in the reciprocal of a cross. 
Biffen (4) in an interspecific cross 
between Polish, an early wheat, and 
Rivet, a late wheat, concluded that 
earliness was dominant. Freeman 
( 14 ), in a cross between durum and 
common wheat, found in F 2 and F 3 
that the average date of heading, while 
intermediate, was nearer that of the 
late parent, indicating that lateness is 
at least partially dominant. Thomp¬ 
son (34) made numerous crosses be¬ 
tween eight varieties of wheat ranging 
from very early to late. In the F x 
nearly all crosses ripened near the 
mean of the later parent. In the F 2 
the great majority of plants were inter¬ 
mediate between the parents, indicat¬ 
ing blending. The apparent domi¬ 
nance of lateness in F x could be explained 
only as due to heterosis or hybrid vigor. 
The further results of individual crosses 
were explained on the “multiple deter¬ 
miner hypothesis of blending. ” Bryan 
and Pressley (5), in a cross between 
Sonora and Turkey, found the F x 
intermediate in time of heading be¬ 
tween the parents and the F 2 majority 
inclined toward the late parent. 
Florell (13) in a Sunset-Marquis cross 
concluded earliness to be dominant 
from F 2 “in the proportion of 3.11 to 
0.89, indicating one allelomorphic pair 
of factors, with possibly a number of 
minor modifying factors. ” ' 
