INFECTION EXPERIMENTS WITH TIMOTHY RUST 



By E. C. Stakman, Head of the Section of Plant Pathology and Bacteriology, and 

 Louise Jensen, Mycologist, Division of Botany and Plant Pathology, Department 

 of Agriculture, University of Minnesota 



INTRODUCTION 



There is some diversity of opinion as to whether or not timothy rust 

 should be regarded as a distinct species. Eriksson and Henning (2, p. 

 140-142)* in 1894 designated it "Puccinia phleipratensis Eriks. u. Henn." 

 Johnson (4) decided that timothy rust in this country was the same as 

 that in Sweden and favors giving the fungus specific rank. Kern (5, 6), 

 on the other hand, thinks it should be considered as a physiological 

 species, or, at most, a variety or subspecies. 



It is therefore of interest to know the infection capabilities of the rust. 

 Eriksson and Henning (3, p. 136-141), reported the successful infection of 

 rye (Secale cereale) and oats {Avena sativa), but none of wheat {Triticum 

 vtilgarc) or barley (Hordewn vulgare). Johnson (4, p. 9) obtained results 

 confirming those of Eriksson and Henning. Johnson also succeeded in 

 successfully infecting a number of grasses. He found that the rust would 

 not transfer directly to barley, but if transferred first to oats and then to 

 barley infection resulted. In the same way Dactylis glomerata acted as a 

 bridging form between timothy and wheat. Mercer (7) was unable to 

 obtain successful infection on wheat, rye, and various grasses as a result 

 of inoculations made with timothy-rust urediniospores. 



The inoculations made by the writers were all on seedlings. The leaves 

 were first thoroughly moistened either with an atomizer or by rubbing 

 water on with the fingers. The spores were applied with a flat inoculating 

 needle. The plants were then placed in shallow pans of water and kept 

 covered with bell jars for 48 hours. The grass seeds were obtained from 

 the Minnesota Seed Laboratory. The following varieties of cereals were 

 used: Oats, Improved Ligowa, Minn. No. 281; barley, Manchuria, Minn. 

 No. 105; wheat, Bluestem, Minn. No. 169; rye, Swedish, Minn. No. 2. 



RESULTS OF INOCULATIONS 



The writers made a number of inoculations with timothy-rust uredini- 

 ospores, the results of which are given in Table I. 



1 Reference is made by number to " Literature cited," p. 216. 



Journal of Agricultural Research, Vol. V, No. 5 



Dept. of Agriculture, Washington, D. C. Nov. i, 1915 



Minn. — 6 



(211) 



