May 17, 1924 
Resistance of Oat Varieties to Stem Rust 
713 
representatives of all available species of Avena, and all of the varieties that 
proved resistant to the oat stem rust collected in Berkeley. 
The experiments were made on seedlings in the greenhouse. Nine pots of 
seedlings of each variety were grown, one for each collection of rust. All were 
inoculated on the same day, placed under bell jars in the cages for 48 hours, the 
bell jars then removed and the plants allowed to grow in the pots. At the end 
of two weeks the plants were studied and rust infection recorded, and the rusted 
leaves packeted and pressed. On completion of the first series the entire experi- 
i 
2 
3 
4 
5 
Wfrv>"' ct 
6 
1* Eureka 
c, Bodgaland 
% % Woodland 
, Givi'S 
5, Berkeley 
Salinas 7 
5* Balboa Park 
Fig. 1 .—Map of California showing, by the shaded areas, the distribution of oat stem rust in California 
in 1919, and by numerals, the points where the nine collections of rust were made 
ment was repeated. The second experiment was not completed until late in the 
fall of 1920, when the cooler weather and reduced light proved unfavorable for 
the development of the rust. These data, therefore, were discarded and this 
part of the work was repeated in the spring of 1921. 
The results are given in Table IV and show a remarkable uniformity in the 
reaction of any variety of oats to the strains of rust from different localities. In 
general, the varieties in the first experiment that were susceptible to the rust 
collected at Berkeley proved equally susceptible to rust from the other sources, 
and the varieties resistant to the Berkeley rust proved resistant to the nine col¬ 
lections from other localities. 
