A STUDY OF RUST RESISTANCE IN A CROSS BETWEEN 
MARQUIS AND KOTA WHEATS ‘ 
By H. K. J 1 ayis;S, Head of Section of Plant Breeding, Division of Agronomy and Farm 
Management, Minnesota Agricultural Experiment Station, and Collaborator, Office of 
Cereal Investigations, United States Department of Agriculture, and O. S. AamodT, 
Assistant Pathologist, Office of Cereal Investigations, United States Department of 
Agriculture f J 
INTRODUCTION 
A knowledge of the mode of inheritance of certain plant characters is 
essential if the breeder is to outline his particular problem. Accord- 
ingly one of the first steps in the investigations carried on for the purpose 
of producing rust-resistant spring wheats has been to determine the 
genetic possibilities of attaining the desired end. 
Several years ago it was a common belief that the rust organism changed 
its infection capabilities so rapidly as to seriously interfere with the pro¬ 
duction of rust-resistant wheat. The investigations of Stakman and his 
coworkers (6, 7, and sy at the Minnesota station have proved that the 
variable results which have been obtained under field conditions are due 
to numerous biologic forms of rust which can only be differentiated by 
their manner of infecting particular pure lines of wheat. This has led 
naturally to the survey to determine the prevalence of particular rust 
forms and to the use of these forms in breeding experiments. The method 
is to determine those wheat varieties which are resistant to particular 
rust forms and then by means of crosses to build up desirable rust-resistant 
varieties. 
Kota (9) is the only rust-resistant spring common wheat which so far 
has been discovered, except for certain recently produced hybrids. 
Under humid conditions, however, Kota does not yield as well as Marquis 
and is seriously lacking in strength of straw. 
The purpose of this paper is to present certain studies of a cross between 
Kota and Marquis which were carried on with the hope of solving the 
following questions : 
1. Is the resistance of Kota to different biologic forms due to a single 
genetic factor, as in the case of Kanred ? 
2. Given Kota and Marquis, which react reciprocally to two biologic 
forms of rust, is it possible to produce from a cross of Kota and Marquis 
a variety resistant to both biologic forms ? 
3. To determine the possibility of using the reaction of Fg seedlings in 
the greenhouse to particular biologic forms of stem rust as a means of 
isolating Fg families which have the resistance of the Kota parent under 
field conditions. 
1 Accepted for publication Feb. 20, 1923. Cooperative investigations between the Sections of Plant 
Breeding and Plant Pathology of the Minnesota Agricultural Experiment Station and the Ofl&ce dt Cereal 
Investigations, Bureau of Plant Industry, U. S. Department of Agriculture. 
Published with the approval of the Director of the Minnesota Agricultural Experiment Station as paper 
No. 350 of the Journal ^ries of the Minnesota station. 
* Rderence is made by number (italic) to “Literature cited,’* * p. 1012, 
Journal of Agricultural Research, 
Washington, D. C. 
afe 
Vol. XXIV, No. z9 
June 23,1923 
Key No. G^3r4 
43326—23 - 4 
(997) 
