INFECTION OF TIMOTHY BY PUCCINIA GRAMINIS 



By E. C. Stakman, Head of the Section of Plant Pathology, and F. J. PiemeisEL, 

 Research Assistant, Division of Plant Pathology and Botany, Department of Agri~ 

 culture, University of Minnesota l 



It has been shown a number of times that Puccinia phleipratensis 

 Eriks. and Henn. can infect oats (Avena saliva) and rye (Secale cereale) , 

 and it has also been shown recently that it can infect barley (Hordeum 

 vulgare; (8, p. 213). 2 Inoculation of timothy {Phleum pratense) with 

 Puccinia graminis was reported by Eriksson (2, p. 71), Johnson (3, p. 9), 

 Mercer (6, p. 22), Stakman and Jensen (8, p. 213), and others as giving 

 only negative results. Carleton, however (1, p. 62), succeeded in infect- 

 ing Phleum asperum with P. graminis avenae. 



The timothy-rust problem offers a good field for investigating the 

 possible origin and developmental tendencies of biologic forms. The 

 rust can infect oats, rye, barley, and a number of wild grasses; but 

 morphologically it differs from P. graminis, and its ability to infect 

 barberry (Berberis vidgaris) regularly is still a matter of doubt (3, p. 11). 

 From its close similarity to P. graminis avenae, however, it seems reason- 

 able to suppose that it may possibly have developed from some form of 

 P. graminis. Since P. phleipratensis resembles P. graminis avenae 

 parasitically more closely than any other biologic form of P. graminis, 

 it would seem that infection of timothy with P. graminis avenae might 

 be possible. For this reason the writers made a very large number of 

 inoculations on a number of strains of timothy. 



All inoculations were made on seedlings from 3 weeks to 3 months old. 

 The leaves were first thoroughly moistened and then inoculated heavily 

 with urediniospores of P. graminis avenae originally isolated from Dacty- 

 lis glomerata and then kept on oats in the greenhouse for 14 months, 

 having been transferred 30 times during that period. The rust had 

 been used extensively in a large number of inoculation experiments, 

 and the fact that it was a normal strain of P. graminis avenae had been 

 well established. After inoculation the pots containing the seedlings 

 were put in pans containing a small amount of water and were then 

 kept covered with bell jars for 48 hours. At the end of that time they 

 were removed and kept on an ordinary greenhouse bench. Inocula- 

 tions were made with other biologic forms of P. graminis also; none 

 of these, however, resulted in infection, therefore serving as checks. 

 The "ordinary" timothy seed used was obtained from the Minnesota 



1 In cooperation with the Office of Cereal Investigations, Bureau of Plant Industry-, United States 

 Department of Agriculture. 



2 Reference is made by number to " Literature cited," p. 816. 



Journal of Agricultural Research, Vol. VI, No. 21 



Dept. of Agriculture, Washington, D. C. Aug. 21, 1916 



fa Minn. — 92 



52174°— 16 2 



(813) 



