June 33,1933 
Rust Resistance in a Marquis-Kota Cross 
999 
The brief outline given shows the present status of the problem, the 
mode of attack being to build up synthetically, by certain crosses, wheats 
which are resistant to as many biologic forms as possible. For this mode 
of attack a knowledge of the number and nature of the inherited factors 
is essential. 
MATERIAL AND METHODS 
Certain general methods of work have been used as in previous studies. 
For this reason only brief descriptions will be made. 
Pure lines of the parental varieties were used in making the crosses. 
The Fj generation plants were grown in the greenhouses^ at Washington, 
D. C., during the winter of 1920-21 and the Fj generation was grown 
during the summer of 1921. The season was a very unfavorable one and 
the seed produced was rather badly shrivelled in certain cases. Indi¬ 
vidual plant data on spike characters, average seed length, seed plump¬ 
ness, and seed texture were taken and the Fg seedlings obtained from 
sowing seed of individual Fg plants were inoculated in the greenhouse 
with the rust forms chosen. 
In deciding which rust forms ^ to use, a study was made of the degrees 
of infection of seedlings of Marquis and Kota when inoculated at the 
same time and handled in a similar manner. 
Eleven biologic forms were available in the greenhouse and all were 
used in inoculations for the purpose of discovering two to which the two 
wheat varieties reacted reciprocally. The reactions obtained on Marquis 
and Kota are given in Table I. AJthough Kota is rather highly resistant 
as tested under field conditions, the difference in seedling infection of 
Marquis and Kota in the greenhouse is not very great. In nearly all 
cases, however, where there is a difference, Kota shows a lower degree 
of infection than Marquis. The meaning of the symbols used to designate 
the types or degrees of infection is given after Table I. 
TablB I .—Reaction of Kota and Marquis to 11 forms of stem rusty expressed by type of 
infection produced 
Type of infection produced by biologic form of rust No.— 
Variety. 
I. 
III. 
IX. 
XVII. 
XVIII. 
XIX. 
XXI. 
XXVII. 
XXIX. 
XXXII. 
XXXIV. 
Marquis.. 
4 
4 ~ 
3 
4 
4 
I and 2 
4 
2 + 
4 
3 + 
3 + 
Kota. 
3 + 
3 + 
3 
4— 
3 
3 
3 + 
0 
3 + 
3 
3 
8 The writers are indebted to Mr. J. Allen Clark, of the Office of Cereal Investigations, for growing the 
Fi generation and returning seed of the same. . , 
< The biologic forms used were obtained from M. N. Levine, who kindly made them available for our use 
