INFLUENCE OF TEMPERATURE ON THE SPORE GER¬ 
MINATION OF USTILAGO 2 EAE ‘ 
By Edith Seymour Jones 
Formerly Scientific Assistant, Office of Cereal Investigations, Bureau of Plant Industry, 
United States Department of Agriculture 
Temperature has been regarded by investigators as important among 
the environmental conditions influencing the infection of corn by Ustilago 
zeae (Beckm.) Unger. Maire (5)^ found that the spores of the corn smut 
fungus ''germinate more quicldy if the temperature is a little raised (20^ 
to 25®)” and that the optimum temperature for sporidial and filamentous 
development is 20° to 25^ C. Piemeisel (7), in considering the "phenome¬ 
non of infection and the optimum conditions for the propagation of the 
fungus/' found the optimum temperature for the budding of sporidia to 
lie between 20° and 26*^ C., the maximum at about 40^^ and the thermal 
death point near 46°. He also found that incubation at 24° to 38° did 
not seem to influence the rate or amount of germination of the smut 
spores. 
As the germination of the spores themselves would seem to be at least 
as significant as the budding of sporidia, and as the above investigators 
do not give detailed experiments on this stage of fungal activity, a study 
of the influence of temperature on the spore germination of Ustilago z^ae 
was undertaken in order to throw additional light upon the relation of 
temperature to this early, significant stage in the life history of the 
fungus. The studies of which the results are presented in this paper have 
been carried on under the direction of Dr^ L. R. Jones. 
In searching for suitable media for spore germination it was attempted 
to duplicate natural soil conditions. Brefeld (^, p. 67-75) performed 
experiments which indicated that the germination of the Ustilago zeae 
spores takes place in the soil. The conception of soil, especially that 
containing manures, as a usual medium of germination of the spores ajso 
has been held even down to the present time. In attempting to find a 
soil medium like that obtaining in nature, the method of Thompson (8) 
was tested. When a tap-water suspension of spores was poured onto 
loam, no germination took place, whereas, when a suspension of spores 
in Pasteur's solution was introduced in the same way, germination fol¬ 
lowed. It seemed that the conditions for spore germination in such soil 
were not suitable, whereas they were satisfactory in the Pasteur liquid. 
In an attempt to find a soil on which the spores would germinate, seven 
modifications of loam and manure were employed, and the spores of 
TUletia tritici (Bjerk.), Wint., were used as controls. On one pot which 
contained cow manure and loam, 1:2, there was considerable germina¬ 
tion, and on another pot, one germinating spore was observed. Another 
test gave slight germination. In all these tests the bunt spores germi¬ 
nated abundantly, but, as a result of all the 27 attempts to germinate 
the spores of Ustilago zeae on soil, no satisfactory method was found. 
1 Accepted for publication Aug. 21, 1922. 
The investigations, the results of which are presented in this paper, were conducted cooperatively by the 
OflSce of Cereal Investigations, Bureau of Plant Industry, and the Department of Plant Pathology of the 
Wisconsin Agricultural Experiment Station. 
* Reference is by number (italic) to “ Literature dted,’* p. 596-597. 
Journal of Agricultural Research, 
Washmgton, D. C. 
aee 
( 593 ) 
Vol. XXIV, No. 7 
May 19, 1923 
Key No. G-303 
