The culture of cereal rusts in the greenhouse 
F. D. FROMME 
The desirability of maintaining cultures of parasitic fungi on 
the living host in the greenhouse for purposes of study and physio- 
logical experimentation is obvious, particularly so with those obli- 
gate forms that cannot be cultivated on artificial media. Methods 
of culture of the powdery mildews of the grasses and other 
members of the Erysipl , and of a species of Cystopus, etc., 
Peronosporaceae, have been placed on an exact basis by the work 
of Reed (28, 29) and Melhus (23). No exact data of this nature, 
however, are available for the rusts. Although a vast number of 
infection experiments on this group have been made in recent years, 
these have dealt only incidentally with conditions governing spore 
germination, infection, and spore formation, and in many cases 
our knowledge on these points is based on field experiments con- 
ducted under conditions not subject to rigid control. There are 
a great many scattered details in the literature as to conditions 
affecting the development of the rusts. I shall summarize o 
those that bear more especially on the problems of growing rusts 
in the greenhouse. 
Smith (33) found that dew is of more importance in determining 
the prevalence of asparagus rust than rainfall. When little dew 
is formed infection cannot occur and sporulation may be checked, 
or altered, with a substitution of the teleuto for the uredo stage. 
This may occur in midsummer on the vigorously growing host as 
the result of excessive atmospheric dryness. He states, moreover, 
that abundance of soil moisture, instead of favoring rust develop- 
ment, acts as a check by giving the host greater vitality. This is 
in agreement with earlier observations by Stone and Smith (34, 
35). They found asparagus beds on light, dry soil heavily rusted 
while those on heavy, moist soil were comparatively free from 
rust. Sirrine’s (32) observations also support the conclusion 
that dew is the most important agent in the spread of asparagus 
rust. 
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