44 
BULLETIN 1403, U. S. DEPARTMENT OF AGRICULTURE 
parents have been approximately reached by F 3 strains, but not ex- 
ceeded significantly except under unfavorable conditions. This 
blending inheritance apparently is due to multiple genetic factors. 
YIELD 
SO 
Yield is a character complex, the product of genetic and environ- 
mental factors. The morphological and quantitative characters 
previously discussed are measures of preliminary plant response and 
are important because of their relationship to yield and quality. 
Yield is the end result of agronomic research. Beaven (1) has 
stated that "the problem of the cereal breeder is to discover the 
relation between the different structures of the individual plant 
and the probable quantity of salable produce per acre.*' This 
has been one of the primary objects of the present study. 
Grain yields on a plant basis in the F 2 and F 3 generations and on 
a nursery-row basis in the F 3 generation were recorded. Yields were 
obtained from defi- 
nitely spaced plants, 
which were harvested, 
threshed, and weighed 
individually. The ¥ 2 
data from Bozeman 
and Moccasin are 
given in Table 41 and 
the Bozeman results 
are shown graphically 
in Figure 9. Unfortu- 
nately, as previously 
stated, the parents 
were not grown with 
this generation at 
Moccasin. 
The Bozeman data 
show that in the F 2 
generation the hv- 
brids averaged con- 
siderably above either 
parent in yield . Mar- 
quis slightly out- 
yielded Hard Federation, but not by a significant amount. There 
is a consistent difference in the yield of reciprocal crosses at the two 
stations in that the Marquis X Hard Federation crosses outyelded 
those of Hard Federation X Marquis. For the Bozeman da^a the 
difference, 0.34±0.11, is significant; but for the Moccasin dita the 
difference, 0.45 ±0.28, is only 1.6 times its error. The coefficients of 
variation which follow show that the F 2 hybrids are less variable in 
yield than either parent. 
Coefficient of v action 
F 2 hybrids 28. 267 ±(. 557 
Hard Federation 34. 470 ±1. 661 
Marquis 43. 845^2. 091 
Nursery-row yields of F 3 strains and of parent checfe were com- 
puted to an acre basis for Bozeman and Moccasin. Because of the 
dwarf plants occurring in some F 3 strains, a uniforn number of 
v/= 
ft 
r s 
&GZ&AZ4// 
f 
1 r 
X 
v 
/ 
c>^ 
-&- 
/ 
^ 
^* 
*•» — 
%so 
/ 3 jF 7 & // /S /& /7 /& 2/ 
Fig. 9.— Frequency distribution of F2 and F3 hybrid wheat plants 
and the range of variation of the Marquis and Hard Federation 
parents, together with their average yield at Bozeman, Mont., 
in 1923 and 1924 
