June 33,1933 
Rust Resistance in a Marquis-Kota Cross 
1007 
acters. Progenies of these were grown in 1922 in the field and the rust 
reaction determined. Eleven of the 47 families were resistant, 14 were 
semiresistant, 4 were susceptible, and 12 were heterozygous. If the 
same relative proportion of the entire 353 resistant families had bred 
true to resistance there would have been 82 out of 666 Eg pl^-nts that 
were homozygous in their resistance to all eight biologic forms. This is 
a ratio of i homozygous resistant to 8.1 of other types, which is very 
similar to the previously discussed result of the inoculation of 206 Fg 
families of which 28 bred true for the Kota type of resistance. 
rnn greenhouse test as a means oe isoeating eines resistant in 
THE EIEED 
One of the purposes of a study of the greenhouse reactions to Forms 
XIX and XXVII was to determine the possibility of using this test as a 
means of isolating lines which would exhibit the Kota type of resistance 
in the field. Fifty-two families whose reactions to Form XIX were 
known in the greenhouse and 48 families whose reactions to Form XXVII 
were known were grown in the field nursery in 1922 and classified under 
field conditions as resistant, near-resistant, heterozygous, and suscept¬ 
ible, as shown in Table VIII. 
Table VIII. —Distribution into classes according to reaction in the greenhouse of 
seedlings from Fg plants in relation to behavior of Fg families in the field rust nursery 
under artificial epidemic conditions 
A study of the results shows that the greenhouse reactions to the 
biologic Forms XIX or XXVII can not be used to determine which 
families will exhibit the Kota type of resistance to several biologic 
forms in the field. Thus of the five families which gave the Marquis 
type of reaction to Form XIX in the greenhouse, namely, the IR group, 
none bred true for resistance under &ld conditions. Similarly, of the 
22 families which gave the Kota type of reaction in the greenhouse and 
which were placed in the IS group, only 3 proved resistant in the field. 
The reaction of Kota to Form XXVII was of the immune or R type. 
Eight hybrid families of this type were grown in the field and only one 
proved as resistant as Kota. These results are further evidence which 
proves that the resistance of Kota to several biologic forms of stem rust 
is due to more than a single genetic factor. 
