458 
Journal of Agricultural Research 
Vol. XXIV, No. 6 
Hayes, Parker, and Kurtzweil (7) recently studied the inheritance of 
resistance and susceptibility, to what apparently was a single biologic 
form, in crosses between common and durum wheats and common wheat 
and emmer. They showed that the inheritance of resistance and 
susceptibility to stem rust was not the same in different crosses. In the 
durum-common cross, susceptibility appeared to be dominant while in 
the emmer-common cross the was resistant, but not as resistant as the 
emmer parent. There was some linkage in transmission between the 
emmer and durum types and resistance to stem rust. Resistant emmer 
and durum types were very common, while it was quite difficult to 
obtain resistant common wheats. 
Puttick (jj) reported the results of a study on the reaction of the Fg 
plants of a cross between two varieties of wheat which react reciprocally 
to two biologic forms of stem rust. Many gradations in reaction to both 
forms of rust appeared, varying from complete susceptibility to complete 
immunity. 
Extensive rust surveys have been made during the last few years. 
The prevalence, distribution, and virulence of the various biologic forms 
of Puccinia graminis triiici are now being ascertained and, for all practical 
purposes, the parasitic effect on the hosts seems to be constant (id). The 
plant breeder now has a definite basic foundation for the development of 
varieties resistant to stem rust. 
Twenty-one biologic forms ^ of rust have been found in the upper half 
of the Mississippi Valley. As the winter wheat, Kanred, is resistant to 2 
of these forms and immune from 11, the value of this variety in breeding a 
rust-resistant spring wheat is apparent. If there could be isolated from 
the progeny of a Kanred-Marquis cross, a spring wheat which would 
be resistant to some or all of the forms to which the winter parent is 
resistant, one step would be accomplished of the many needed to produce 
a generally resistant variety. 
Kanred is a true winter wheat which, when sown in the spring, at 
University Farm, St. Paul, Minn., produces only an occasional head 
late in the season and does not set seed. Marquis is a true spring wheat, 
which, when sown in the fall, seldom, if ever, lives through the winter. 
Growth habit, as used in this paper, is meant to indicate that general 
difference which exists between true spring and true winter varieties in 
their ability to produce heads normally when sown in the spring of the 
year (PI. i. A). 
Apparently few investigations have been made on the inheritance of 
growth habit. Innumerable observations have been reported in litera¬ 
ture on the differences in heading period and maturity between varieties 
in both spring and winter groups. These differences, while they may be 
of the same general nature as winter habit, are comparatively very mi¬ 
nute, but they are constant, as was shown by Fruwirth (j) in 1918. 
A single head of wheat was selected and divided into two parts. One- 
half of this seed and its progeny was constantly sown in the fall and 
the other half in the spring. This process was continued for 8 years. 
The two lots of seed were then sown together in both the fall and spring 
and the growth habits compared. The period of blossoming and ripening 
was the same for all plots, showing that selection within a pure line was 
of no value. 
^Unpublished data furnished by E. C. Stakman and M. N, Levine. 
