June 33 , X933 
Rust Resistance in a Marquis-Kota Cross 
1003 
RI^ACTION OF Fg SEKDI^INGS AND THFIR PARENT VARIETIES TO BIOLOGIC 
FORMS XIX AND XXVII 
Pots of the parent varieties, Marquis and Kota, inoculated and handled 
in the same manner as the hybrid P3 families, were used as controls. In 
order to assist in the study the parents and the various Fg families were 
classified into groups on the basis of their resistance or susceptibility to 
infection by these two forms of rust as follows: 
Classes of resistance and susceptibility to infection in the Marquis-Kota cross when Fg 
seedling families and the parent varieties were inoculated with biologic Forms XIX 
and XXVII in the greenhouse in the winter of ig2i-22 
BIOLOGIC FORM XIX 
IR== Resistant in classes of infection types i to 2, or that of the Marquis parent. 
HR=Heterozygous with the Marquis or types i and 2 reaction dominant. 
H== Heterozygous with the Kota or type 3 reaction dominant. 
HS=Reaction mainly of the Kota type, type 3, with an occasional plant of the 
Marquis type of reaction. 
IS=Reaction of type 3, like the Kota parent. 
BIOLOGIC FORM XXVII 
R=Infection of type o, or the immunity of the Kota parent. 
IR=Reaction of type 2, the resistance of the Marquis parent. The uredinia were 
somewhat larger than for the normal type 2 infection. 
Hi == Heterozygous with reactions of types o and 2. 
H2=Heterozygous with reactions of types o, 2, and 4. 
H3=Heterozygous with reactions of types 2 and 4. 
H4=Heterozygous with reactions of types o and 4. 
S=Susceptible with reaction in type 4 only. 
The results obtained from inoculating the parents and Fg hybrids 
with biologic Form XIX are given in Table V. 
Table V .—Distribution of Fg seedlings of the cross between Kota and Marquis according 
to types of infection caused by biologic Form XIX 
Classes of parents and 
Fs crosses. 
Distribution by types of infection. 
Num¬ 
ber of 
plants. 
Num¬ 
ber of 
fami¬ 
lies. 
0 
—I 
I 
—2 
3 
3 + 
—3 
3 
3 + 
Fg families IR. . . . 
Fg families HR.... 
Fg families H. 
Fg families HS.... 
R fatni 1 ip<s 
4 
9 
23 
7 
35 
5 
16 
17 
I 
I 
170 
147 
118 
20 
18 
IS 
8 
3 
14 
13 
15 
150 
163 
187 
17 
39 
15 
27 
3 
13 
123 
45 
131 
33 
lOI 
768 
381 
2,117 
83 
IS 
962 
1 
25 
2 
412 
478 
1,269 
477 
2,308 
264 
627 
16 
978 
40 
44 
114 
45 
212 
23 
50 
I 
81 
Marquis IR. 
Marquis HR. 
Kota HS . 
.... 
215 
326 
I 
I 
39 
12 
40 
107 
3 
9 
Kota TvS .... 
13 
3 
The infection of the Kota parent fell within type 3 with the exception 
of one plant which had a type i infection. With the conditions under 
which the studies were made, occasional infection with a different 
biologic form could not be avoided. The infection of the Marquis parent 
fell mainly within types i and 2, although there were 118 plants out of 
891 which showed infection of type 3. 
