June 23, 1923 
Inheritance of Resista^ice to Puccinia graminis 
981 
forms of rust were obtained. Some of the progeny appeared to be 
resistant to both forms. 
More recently Melchers and Parker {22) found that a single factor 
was responsible for the resistance in crosses of Kanred with Marquis, 
Preston, and Haynes Bluestem, which were inoculated with a single 
form of rust. Segregation in F2 was in a 3:1 ratio of resistant and 
susceptible plants. ‘ The results were verified by carrying the study 
through the third generation. 
Aamodt (j, 2), in 1921, studied the inheritance of resistance to several 
biologic forms of P. graminis tritici in a cross between Kanred, a winter 
wheat, and Marquis, a spring-sown variety. Kanred is resistant to a 
number of biologic forms whereas Marquis is susceptible to most of them. 
Fg seedling plants inoculated with a form of rust to which Kanred was 
immune and Marquis susceptible proved either resistant or susceptible. 
Families, homozygous for spring habit of growth and for resistance to 
all the forms of rust to which Kanred was resistant, were obtained in 
the Fg. Here a single factor apparently determined the reaction to 
several biologic forms, to ii of which Kanred is immune. 
Of the 37 known biologic forms of stem rust 21 were found in the area 
where hard red spring wheats are grown. ^ The most recent study in 
disease-resistance breeding at the Minnesota station shows the possibility 
of synthetically producing a desirable vulgare variety of wheat that will 
be resistant to all of these biologic forms {17). This is to be accom¬ 
plished by means of several crosses and double crosses between varieties 
having the desired resistance and those having the necessary bread-wheat 
qualities for yield, milling, baking, etc. 
In the present investigation use was made of a cross between two 
varieties of durum wheat which react reciprocally to two biologic forms 
of rust, each being resistant to the form to which the other is susceptible. 
It was hoped that some Fg families would prove resistant to both forms 
of rust. In addition to a study of the genetic factors concerned with 
resistance the relation of seed color to rust resistance was also considered. 
That resistance to several biologic forms is governed by a single factor, 
in the Kanred X Marquis cross, indicates the importance of learning as 
much as possible about the inheritance of resistance to various rust 
forms in different crosses. 
MATERIALS AND METHODS 
The Fg families ® of two T. durum crosses. Kubanka 8 (C. I. 4063) X 
Pentad (C. I. 3322) and Mindum (Minn. No. 470) X Pentad, were used. 
Kubanka No. 8 is a white-seeded selection from common Kubanka 
(C. I. 1440). Pentad is a red-seeded variety selected at the North 
Dakota station. Mindum is a white-seeded selection of the Arnautka 
type. Seedling plants from each Fg family were inoculated in the green¬ 
house with two biologic forms of P. graminis tritici. The crosses were 
made in 1920, and &e F^ generation was grown in the greenhouse at 
Washington, D. C., during the winter of 1920-21. The Fg generation 
was grown in the plant-breeding nursery at University Farm, St. Paul, 
Minn., during the 1921 season, the plants being harvested individually. 
♦ Unpublished results of Stakman and Levine, 
5 The term “ Fa family” is used in this article for the seedling plants grown from the seeds of a single 
F2 plant. 
