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Journal of Agricultural Research 
Vol. XXIV, No. i» 
QUESTION AS TO WHETHER THE RESISTANCE TO FORM XIX AND FORM XXVII 
CAN BE combined IN A SINGLE VARIETY 
In order to build up wheats resistant to all biologic forms, it is neces¬ 
sary to combine in a single variety the resistance exhibited by different 
wheat varieties to particular biologic forms. The reactions of Fg families 
to Forms XIX and XXVII are correlated in Table IX. 
Table IX. —Distribution of families classified according to reaction to form X/X 
in relation to reaction to Form XXVII 
Reaction to Fonn XXVII. 
Reaction to Form XIX. 
IR. 
HR. 
H. 
HS. 
IS. 
Total. 
3 
9 
13 
5 
44 
74 
4 
2 
I 
0 
I 
8 
6 
6 
12 
4 
14 
42 
7 
II 
13 
7 
29 
67 
H3. 
I 
5 
15 
3 
13 
37 
H4. 
3 
9 
27 
IS 
59 
113 
I 
2 
8 
I 
19 
31 
Total. 
25 
44 
89 
35 
179 
372 
Three out of a total of 372 families proved immune from Form 
XXVII and were resistant to Form XIX, and 4 families were resistant 
to both biologic Forms XIX and XXVII. It is possible, therefore, to 
combine in a single variety the resistance of the Marquis parent to Form 
XIX, and the immunity of the Kota parent from Form XXVII. These 
facts give further hope for the belief that resistance to different biologic 
forms exhibited by different wheat varieties is due to independently 
inherited Mendelian factors or that the linkage of these factors is so 
slight that crossovers frequently occur. From the genetic standpoint 
the facts so far learned give reason for the belief that a wheat variety can 
be produced which will be resistant to all biologic forms of stem rust. 
CORRELATION between MORPHOLOGIC AND SEED CHARACTERS AND RUST 
R^ISTANCE 
The Fg plants which were the parents of the Fg families tested under 
field conditions were classified as normal awnless or bearded and dwarf 
awnless or dwarf bearded. For the purpose of determining whether 
there was any marked correlation between these characters and reaction 
to rust, the reactions of these separate morphologic groups to Form XIX 
and Form XXVII have been arranged in correlation, as shown in Tables 
X and XI. 
