JOlMALOFAGlflaiTlAlRESEARCH 



Vol.. X Washington, D. C, August 27, 1917 No. 9 



BIOLOGIC FORMS OF PUCCINIA GRAMINIS ON CEREALS 



AND GRASSES^ 



By E. C. Stakman, Headofthe Section ofPlatit Pathology, Division of Plant Pathology 

 and Botany, Department of Agriculture, University of Minnesota, and F.J. PlEMEiSEL, 

 Scientific Assistant, Office of Cereal Investigations, Bureau of Plant Industry, United 

 States Department of Agriculture 



COOPERATIVE INVESTIGATIONS BETWEEN THE AGRICULTURAL EXPERIMENT STATION 

 OK THE UNIVERSITY OF MINNESOTA AND THE BUREAU OF PLANT INDUSTRY OF THE 

 UNITED STATES DEPARTMENT OP AGRICULTURE 



INTRODUCTION 



The question as to which biologic forms of Pticcinia graminis Pers. 

 occur on wild grasses is important. Considerable work has been done on 

 the biologic forms of stemrust on the common cultivated cereal grasses, 

 and some has also been done on the r.elation of the rust on wild grasses 

 to that on cereals. However, on account of the scientific and practical 

 importance of obtaining further information on the identity of the 

 biologic forms of P. graminis on wild grasses and the importance of 

 determining the degree of plasticity of these forms when subjected to 

 changed environments, preliminary work on the problem was begun at 

 the Agricultural Experiment Station of the University of Minnesota in 

 the spring of 1913. Since 1915 the work has been done in cooperation 

 with the Office of Cereal Investigations, Bureau of Plant Industry, United 

 States Department of Agriculture. The cooperative arrangement has 

 made possible more extensive work and has also given it broader scope. 



The object of the work was to determine first the wild hosts for the 

 various biologic forms of P. graminis. An attempt was made to deter- 

 mine the frequency of association of any given biologic form with a 

 particular host, the possible geographical localization of biologic forms, 

 the possible variation in parasitic capabilities of forms from different 

 hosts and different localities, and the possible relation of the facts 

 obtained to cereal-rust epidemiology. In order to obtain facts of value 

 on the last-named phase of the problem, it was necessary to make obser- 

 vations on the origin of the early spring infections, the relation of bar- 

 berries (Berberis spp.) to the occurrence and behavior of rust, and to 



1 Published, with the approval of the Director, as Paper No. 67 of the Journal Series of the Minnesota 

 Agricultural Experiment Station. 



Journal of Agricultural Research, Vol. X, No. 9 



Washington, D. C. Aug. 27, 1917 



jn Key No. Minn. — 19 



(+29) 



