32 
Journal o f Agricultural Research 
Vol. XXIX, No. 1 
group averaged 23.4 per cent of re¬ 
sistant plants at Mandan and only 
8.1 per cent at St. Paul. 
The susceptible group at Mandan 
showed that F 2 plants having from 16 
to 70 per cent infection produced a 
few resistant plants. All F 2 plants 
grown which had 71 per cent or more 
of infection, did not produce any re¬ 
sistant plants. The susceptible class 
produced as a whole only 2.1 per cent 
of resistant plants. Among the en¬ 
tire 10,042 F 3 plants grown at Mandan, 
1,567, or 15.6 per cent, were classified 
as resistant. 
Of the 75 F 4 selections grown at 
Mandan in 1923, 31 were estimated to 
have an average rust infection of 
15 per cent or less. These were all 
from what appeared to be resistant 
F 3 plants at St. Paul or Mandan in 
1922. Of the 31 only 10 appeared as 
resistant as Kota (average of 5 per 
cent), including 4 which were noted to 
be more resistant. There is evidence, 
therefore, that F 4 strains can be ob¬ 
tained which are homozygous for stem- 
rust resistance. Whether they will be 
as resistant or more resistant than 
Kota under conditions of very severe 
rust remains to be determined. 
YIELD OF PLANTS 
Yield may be considered as a charac¬ 
ter complex affected by environment 
and by most of the morphological and 
physiological characters of the plant. 
Engledow and Wadham (10) state 
that— 
Cereal yield is controlled by a great number of 
factors which are themselves complex and imper¬ 
fectly understood. In approaching the yield prob¬ 
lem it is convenient to arrange these in broad cate¬ 
gories which may thus be designated: (1) Soil, (2) 
climate, (3) agricultural practice, (4) disease and 
damage, (5) botanical variety or form. 
Beaven (3) concludes 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 
saleable produce per acre. The predominant factor 
of productivity in cereals is the seed-forming energy 
of the individual plants composing the crop. 
Yields of F 2 and F 3 plants were ob¬ 
tained in the present study. The plants 
were definitely spaced, harvested in¬ 
dividually, threshed, and the grain 
weighed to tenths of grams. In the 
F 2 yields were obtained at St. Paul and 
Mandan. The data obtained are given 
in Table XXIII and shown graphically 
in Figure 7. 
Table XXIII.— Segregation of 1,699 F 2 plants of the Kota-Hard Federation 
crosses, in comparison with their parents, into 1-gram classes for yield of plant, 
at St. Paid, Minn., and Mandan, N. Dak., in 1922 
Number and percentage of plants 
Source and yield classes (grams) 
F 2 hybrid 
Hard Federation 
Kota 
Number 
Percent¬ 
age 
Number 
Percent¬ 
age 
Number 
Percent¬ 
age 
0. R 
ST. PAUL, MINN. 
28 
5.2 
5 
31.2 
>1.5 
83 
15.3 
7 
43.7 
2.5____ 
91 
16.8 
2 
12.5 
1 
5.6 
3. 5_ _ 
97 
17.9 
2 
12.5 
1 
5.6 
4.5 . 
82 
15.1 
2 
11.1 
5. 5 
67 
12.4 
2 
11.1 
6. 5... 
44 
8.1 
4 
22.2 
7.5 , 
24 
4.4 
2 
11.1 
8. 5... . 
13 
2.4 
3 
16.7 
9.5__ 
7 
1.3 
2 
11.1 
10.5_ . . 
3 
.6 
1 
5.6 
13. 5 
1 
.2 
15. R 
1 
.2 
Total___ 
541 
99.9 
16 
99.9 
18 
100.1 
0. 5.. 
MANDAN, N. DAK. 
16 
1.4 
10 
23.8 
1 
3.3 
1. 5__ 
83 
7.2 
14 
33.3 
2 
6.7 
2. 5_ .. _ 
196 
16.9 
11 
26.2 
10 
33.3 
3. 5_ 
278 
24.0 
5 
11.9 
8 
26.7 
4.5_ _ 
264 
22.8 
2 
4.8 
6 
20.0 
5. 5_ 
166 
14.3 
2 
6.7 
6.5__ . _ __ 
93 
8.0 
1 
3.3 
7.5__ 
35 
3.0 
8.5 . 
17 
1.5 
9. 5 - 
5 
.4 
10. 5_ 
3 
.3 
11.5. 
. 1 
.1 
12. R_ 
1 
.1 
Total_ _ 
1,158 
100.0 1 
42 
1 
100.0 
30 
100.0 
