Methods in Rust Investigations 241 



NOTES ON GREENHOUSE CULTURE METHODS USED 

 IN RUST INVESTIGATIONS/ 



E. B. Mains, Purdue University. 



The methods necessary for tlie production of infections with rusts 

 are relatively simple. Yet, the more intensive and detailed studies, 

 especially in connection with specialized strains and physiological rela- 

 tions, have necessitated certain refinements. These are being developed 

 in various ways in laboratories where such investigations are conducted. 

 In the investigation of the leaf rusts of wheat, Puccinia triticina Eriks., 

 rye, P. dispersa Eriks., barley, P. simjjlex (Korn) Eriks. & Henn., and 

 corn, P. Sorghi Schw., in progress at the Purdue University Agricul- 

 tural Experiment Station, co-operating with the Office of Cereal In- 

 vestigations, of the Bureau of Plant Industry, U. S. Department of Agri- 

 culture, since 1918, it has been necessary to modify certain established 

 culture methods to meet conditions peculiar to the problem. 



This paper has been written primarily with the object of describing 

 such modifications. However, with the idea that it might be made more 

 generally useful, especially for students desiring to undertake some cul- 

 ture work in laboratories where little or no rust research is carried on, 

 descriptions of these modifications, together with reference to methods 

 developed in other laboratories, are incorporated in an account of the 

 general culture procedure employed in this laboratory. This pro- 

 cedure is believed to be similar to that used in most other labora- 

 tories where such studies are in progress. Descriptions of rust-culture 

 methods have been published in numerous journals and bulletins dealing 

 with the results of investigations of many different species of rusts. 

 Papers by Carleton (1903),' Melhus (1912) and Fromme (1913), how- 

 ever, deal primarily with culture methods for this group of parasites. 



1. Collection and Storage of Inoculum. Spores for inoculation pur- 

 poses are relatively easily obtainable. Where the aecia or uredinia 

 occur locally, rusted plants are brought into the laboratory and sow- 

 ings are made with the fresh spores. When the problem involves the 

 study of a rust from various sections of the country as for example the 

 investigation of the occurrence and characteristics of diflfei'ent strains 

 of Puccinia triticina, the fungus causing the leaf rust of wheat, the 

 inoculum may be in transit several days. In the case of this rust, 

 and many of the grass rusts, the spores will remain viable several days 

 if rusted leaves simply are placed in heavy Manila envelopes and mailed. 



It is a mistake to tightly wrap rusted plants in moist or paraffin 

 paper in order to prevent desiccation. Under such conditions, especially 

 during hot weather, more or less heating, fermentation, and molding of 

 the material takes place, which is very detrimental to the viability of 



^ Contribution from the Botanical Department of the Purdue University Asricultural 

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

 U. S. Department of Agriculture, co-operating. 



" Reference, by date, to "Literature Cited." 



"Proc. Ind. Acad. Sci., vol. 33, 1923 (1921)." 

 16—27933 



