Aug. 4 , 1 923 
Resistance in Rye to Leaf Rust 
2 45 
results reported in this paper were obtained through a study of rye 
seedlings in pot culture in the greenhouse, where individual differences 
are more easily distinguishable. The employment of this method has 
resulted in bringing out differences in resistance and gives promise of 
being of considerable importance in the improvement of rye through the 
development of disease-resistant strains. 
DISCOVERY OF RYE RESISTANT TO LEAF RUST 
In the fall of 1920, three kernels from a rye head, supposedly fertilized 
by wheat pollen in the experimental nurseries at Washington, D. C., were 
sown in the greenhouse of the Department of Botany, Purdue University 
Agricultural Experiment Station, at La Fayette, Ind. The resulting 
plants were there inoculated with the leaf rust of wheat, Puccinia triticina 
Erikss., and the leaf rust of rye, P. dispersa. Plants grown from seed 
from an open-fertilized head of the parent rye plant and from the variety 
of wheat from which pollen had been used in pollinating the rye head 
were used as controls. The inoculation with the leaf rust of wheat pro¬ 
duced heavy infection on the wheat control but only slight infection on 
the three supposed hybrids and on the rye control. Inoculation with 
P. dispersa , on the other hand, produced no infection on the wheat con¬ 
trol, while on the rye control, one plant, No. 10, was highly susceptible 
(PI. 1, D) and another, No. 11, showed some resistance (PI. 1, E), as indi¬ 
cated by the hypersensitive areas surrounding the uredinia. The three 
supposed hybrids showed an even greater variation, one plant, No. 7, 
being as susceptible (PI. 1, C) as the susceptible control; the second, 
No. 9, being highly resistant (PI. 1, A), as shown by the definite hyper¬ 
sensitive areas accompanying the uredinia; while the third, No. 8, was 
practically immune (PI. 1, B) showing only a few small hypersensitive 
areas. Thirty-three other plants from open-fertilized seed of the parent 
rye plant were then inoculated with the leaf rust of rye, 19 showing a 
high susceptibility similar to that of plants Nos. 7 and 10, 5 showing 
some slight signs of resistance, 5 showing a resistance similar to Nos. 9 
and 11, and 4 a high resistance similar to No. 8. The similarity in action 
of the supposed hybrids and the plants grown from open-fertilized rye, 
at once threw doubt upon their hybrid nature. When grown to ma¬ 
turity all proved to be pure rye, as was indicated by their reaction to 
the rust. 
SECOND GENERATION RESULTS FROM RESISTANT PLANTS 
The first generation of the progeny from plants 7, 8, 9, and 10 has been 
studied as to susceptibility to leaf rust, in an attempt to throw some 
light on the nature and inheritance of resistance, with the ultimate 
object of obtaining pure rust-resistant strains of rye. In the spring of 
1921, plants 7, 8, 9, and 10 were selfed by bagging the heads of each 
plant separately, and were crossed in various combinations by bagging 
the heads of two plants together in combinations as shown in Table I. 
From the seed obtained from these plants, selfed, crossed, and open- 
fertilized, 596 plants were raised in the greenhouse at La Fayette, Ind., 
in the fall of 1921. Each was grown in a 3-inch pot, and when in about 
the third or fourth leaf, was tested as to its susceptibility to leaf rust. 
After being studied as to their susceptibility, a select few of each of the 
principal types were transplanted to 10-inch pots and were selfed and 
crossed in various combinations again in the spring of 1922. The re- 
