Plant Pathology Conference
Inoculation methods and environmental factors
in relation to covered smut of barley
December 79  1949 John F* Schafer
I* INTRODUCTION
Investigations at the Wisconsin Agricultural Experiment Station by Josephson
(7) in 1941 on the intermediate loose smut of barley and by Schaller (9) in 1946 on
the loose smut of barley added information on epidemiology and the inheritance of resistance. These studies stimulated the undertaking of a parallel study on the third
smut of cultivated barley*, the covered smut caused fcy Patilqgq fc^ffdei (Pers.) Lagerh«
This organism was described by Persoon (8) in 1801, and its present nomenclature
dates from 1889• The covered and loose smuts were first clearly distinguished in
1888 by Jensen (5)* The spores of covered emut germinate by pronyeelia and sporidia,,
and penetration occurs in the young barley seedling.
II. INOCULATION METHODS
Previous work: Satisfactory inoculation by artificial means has been difficult*
Jensen observed that spores adhering externally on the seed did not seem to cause
damage the following season. However, he was able to increase the percentage of
infection by manually removing the floral bracts from the seed prior to dusting with
spores. To eliminate this time taking task Briggs (1) experimented with dehulling
by sulfuric acid* More recently methods of inoculation involving soaking the seed
in a spore suspension, particularly under conditions of partial vacuum, have been
proposed. These were patterned after the method used for loose smut of oats ^
Haarring (4) and have been reported by Tapke and Bever (12) and others.
Present work: Experiments were planned to test the relative effectiveness of
several methods of inoculation. Analysis of preliminary experiments indicated that
those methods tested not invo3-ving removal of hulls from the seed gave significantly
lower percentages of smut than did the method of hand dehulling and dusting with eporss*
The spore suspension method applied by partial evacuation gave lower infection but
higher seedling stand in 1947 and 1949* although appearing to be about equal to the
hand dehulling method in inconclusive tests in 1948* The sulfuric acid dehulling
resulted in excess seedling injury. The use of potassium oxalate to loosen the hulls
prior to inoculation appeared to be of no value*
III. ENVIRONMENT/iL FACTORS
Previous work: Faris (2) studied the influence of soil temperature, moisture,
and reaction in the pre-emergence period and found that high percentages of smutted
plants were obtained at a central range of temperature (10s, 15°$  and 20° C.) and
in acid soil (pH 5) held at 20° and 25° C. at either 40 or 50 per cent moisture holding capacity and also at 10° and 15° C at 50 per cent moisture holding capacity
only. 3y varying the soil temperature during seedling emergence he increased the
percentage of smutted plants* Taylor and Zehner (13) found progressive increase in
percentage of covered smut with increased seeding depth from l/2 to 3 inches. Jones
and Self el Nasr (6) reported that high soil mosture reduced covered smut* Farls (3)
in studying the post-emergence period demonstrated that plants grown in the greenhouse
showed larger amounts of smut than those grown in the field following identical pre-
emergence treatment. B|y impeding either the pre-emergence growth through tamping the
soil or using a heavy soil or the post-emergence growth by pruning the roots Tapke
(10) obtained greater incidence of covered smut. Both Faris (3) and Jones and Self
el Nasr (6) reported that dehulling of the barley kernels resulted in twisted, contorted
seedlings many of which did not reach the soil surface* Tisdale and Tapke (14) found
a similar occurrence with a seedling infecting loose smut, but concluded the injury to
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