AECIAL STAGE OF THE ORANGE LEAFRUST OF 

 WHEAT, PUCCINIA TRITICINA ERIKS.^ 



By H. S. Jackson, Chief in Botany, and E. B. Mains, Associate Botanist, Purdue 

 University Agricultural Experiment Station, and Agents, Office of Cereal Investiga' 

 tions. Bureau of Plant Industry, United States Department of Agriculture ^ 



This paper presents, in part, the results of a study of the leafrusts 

 of wheat, rye, barley, com, and related grasses which was begun in 191 8. 

 One of the important phases of this investigation is the determination of 

 the aecial relationships of the various races or species included in the 

 collective species, Puccinia Clematidis (DC.) Lagerh. (P. Agropyri Ellis 

 and Ev.), and other closely related forms. While a number of the rusts 

 of this group which occur on wild grasses have been connected with 

 aecia, their host limitations and interrelations are not well understood. 

 This study is especially important in the case of the leafrust of wheat, 

 P. triticina Eriks. So long as the aecial stage of this species was un- 

 known, little progress could be made in developing our knowledge with 

 reference to its origin, development, spread, and relation to other rusts. 

 The results of the investigation of the aecial relationship of this rust 

 are presented in the following pages. 



HISTORICAL REVIEW 



Three rusts are known to attack wheat : the black or stemrust, Puccinia 

 graminis Pers. ; the stripe or yellow rust, P. glumarum (Schmidt) Eriks. 

 and Henn. ; and the orange or leafrust, P. triticina. Of these the stem- 

 rust is the only one for which the aecial stage has been determined. 

 This rust was shown by De Bary to have its aecial stage on Berberis 

 vulgaris L., and this relationship has since been demonstrated repeatedly 

 by a number of workers in various parts of the world. The discovery 

 of the place of Aecidium Berberidis Pers. in the life cycle of P. graminis 

 caused De Bary (4, p. 207-211)^ to turn his attention to the study of 

 other grass rusts having incomplete life cycles. This resulted in the 

 discovery that P. rubigo-vera (DC.) Wint. (P. straminis Fckl.) on rye 

 was connected with aecia on Anchusa officinalis and Anchusa arvensis. 

 Sowings made with teliospores from rye resulted in the production of 



' Published with the approval of the Director as a contribution from the Department of Botany, Purdue 

 University Agricultural Experiment Station. Cooperative investigation between the Purdue University 

 Agricultural Experiment Station and the Office of Cereal Investigations, Bureau of Plant Industry, United 

 States Department of Agriculture. 



' The writers wish to acknowledge their indebtedness to various pathologists throughout the country 

 for aid in obtaining material for the cultural studies upon which this paper is based, and to Mr. Forest 

 Fuller, temporary culture assistant during the spring of 1919, and Mr. Emile Mardfin and Miss Florence 

 M. Smith, Scientific Assistants, Ofifice of Cereal Investigations, Bureau of Plant Industry, for assistance 

 in carrying out the cultural investigations. 



' Reference is made by number (italic) to "Literature cited," p. 170-171. 



Journal of Agricultural Research, Vol. XXII, No. 3 



Washington, D. C Oct. 15, 1921 



zz Key No. G-347 



