A MOSAIC DISEASE OF WINTER WHEAT AND WINTER RYE 7 
wheat, and two similar experiments have been conducted with Wis- 
consin Pedigree No. 2 winter rye. The Harvest Queen wheat variety 
commonly develops both rosette and mosaic leaf mottling. It was 
important to determine, therefore, whether rosette would develop in 
Harvest Queen plants when inoculated with juice from a variety 
which develops only mosaic. The Currell variety therefore was used 
as a source of inoculum, because it develops mosaic without rosette. 
The inoculum was prepared by grinding the leaves, sheaths, and 
crowns of infected plants with sterilized fine quartz sand in an 
ordinary porcelain mortar. All roots and old outer leaves and 
sheaths were carefully removed and discarded, and the plants were 
washed thoroughly in tap water to remove any soil particles which 
might adhere to the tissue. The ground pulp and expressed juice 
were introduced or applied into the seedlings near the bases of the 
coleoptiles by means of a sterile needle. A small quantity of absorb- 
ent cotton was then wrapped around the base, of the plant, and this 
was saturated with inoculum. The uninoculated control seedlings 
were treated in a similar manner with the juice and ground tissue 
from healthy Currell wheat plants. 
The seedlings used in the inoculation experiments were in the 
second or third leaf stage of development. Previous to inoculation, 
they were removed from the soil, and all soil was washed from the 
roots and bases of the tillers. After washing they were inoculated 
and returned to disinfected soil to continue their growth. The best 
results haA 7 e thus far been obtained when the inoculated plants were 
grown at air and soil temperatures nearly comparable to those out 
of doors during the fall and early spring growing periods for winter 
wheat. 
The results of these inoculation experiments are given in Table 1. 
It is of particular interest to note that all but one of the Harvest 
Queen plants affected with mosaic in the first five experiments be- 
came dwarfed. They also developed a deep-green color. The leaves 
were very stiff and brittle, and the plants proliferated excessively. 
In fact, these plants presented an appearance (fig. 4, B, C, D) which 
was very similar to, if not identical with, that of plants affected 
with wheat rosette under field conditions. It will be noted that sev- 
eral Harvest Queen plants developed mosaic in experiment No. 7. 
As the plants in this experiment were later severely attacked by 
powdery mildew, it was not possible to keep them for a time suffi- 
ciently long for rosette to develop. Although it is possible that 
mosaic and rosette are produced by separate causal agents and that 
the Currell variety is a carrier of the rosette causal factor, this 
seems doubtful. For the present it seems more reasonable to con- 
sider that both manifestations are due to a single cause. 
Although the percentage of inoculated plants which developed 
mosaic is small, this is not surprising, as the mosaic diseases of other 
grasses and certain dicotyledons have not been transmitted readily 
by means of the expressed plant juice. Also, the winter-wheat plant 
does not develop normally under greenhouse conditions. Further 
studies must therefore be made to determine the influence of environ- 
mental factors on the host as well as on the disease. 
