RUST IN SEED WHEAT AND ITS RELATION TO 

 SEEDLING INFECTION^ 



By Charles W. Hungerford 



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



States Department of Agriculture 



INTRODUCTION 



The fact that the mycelium of rust fungi in some cases may enter the 

 seed and seed parts of various plants and produce spore bodies there has 

 been known for many years and has been referred to by various writers. 

 Differences of opinion have existed, however, as to the importance of 

 this phenomenon in the dissemination of the rust concerned. Aside from 

 the occurrence of rust in and upon these plant organs, other facts have 

 seemed to indicate that rust might be transmitted by means of seed. A 

 number of cases are on record where the uredinial and telial stages of 

 various rusts have suddenly appeared in regions where the aecial host was 

 unknown. Lagerheim {ijY found Puccinia coronata Cda. on oats in 

 Ecuador, and since no species of Rhamnus known to bear the aecia of this 

 rust occur there he concluded that the rust was probably introduced by 

 means of oats brought from Europe. He also reported stemrust doing 

 great damage in Ecuador, although barberry bushes were not present 

 there. According to McAlpine {i8, p. 60), P. graminis is common 

 in Australia, while only a very few hedges of barberry exist and the aecial 

 stage of this rust has never been found occurring naturally upon that 

 continent. Bolley and Pritchard (5, p. 647) quote McAlpine as saying 

 that he is convinced that certain grass seeds secured by him from the 

 United States Department of Agriculture introduced certain rusts into 

 Australia. Among these he named P. coronata Cda. on the grass Beck- 

 mannia emcaeformis and P. montanensis Ell. on wild rye {Elymus cand- 

 densis). Numerous other similar instances could be cited. 



The widespread occurrence of rust epidemics has not been satisfac- 

 torily explained, to some pathologists at least, by our present knowledge 

 of the overwintering of the uredinial stage or by our present knowledge 

 of the importance of infection of wheat by aeciospores from the barberry. 

 These conditions have caused a number of writers to attempt to explain 

 sporadic attacks of rust by a theory of seed transmission. The idea is 



' The investigations reported in this paper were carried on at Madison, Wis., under the direction of the 

 Ofifice of Cereal Investigations, United States Department of Agriculture, Washington, D. C. The writer 

 wishes especially to thank Dr. L. R. Jones and Dr. A. G. Johnson, of the Department of Plant Pathology 

 of the University of Wisconsin, and Dr. H. B. Humphrey, of the Office of Cereal Investigations, United 

 States Department of Agriculture, for helpful suggestions and criticisms during the progress of the work 

 and in the preparation of the manuscript. 



* Reference is made by number (italic) to " Literature cited," p. 275-277. 



Journal of Agricultural Research, Vol. XIX, No. 6 



Washington, D. C. June 15, 1920 



ul (257) KeyNo. G-I9S 



