PHYSIOLOGICAL STUDIES OF BACILLUS RADICICOLA 



OF CANADA FIELD PEA^ 



Martin J. Prucha 



INTRODUCTION 



Ever since the discovery tiiat the formation of nodules on the roots of 

 legumes is associated with a definite microorganism, there have appeared 

 on the market pure cultures of this organism for the artificial inoculation 

 of leguminous plants. Nobbe and Hiltner (1897)^ first caused to be 

 placed on the market a pure culture called nitragin," in which the medium 

 employed was gelatin. The efficiency of the culture was low, and Nobbe 

 and Hiltner explained this by ascribing to the culture a loss of infecting 

 power due to the medium used. Moore (1905) stated, as a result of his 

 work, that the virulence of the organism was impaired when it was prop- 

 agated on nitrogenous media, and consequently he used a nitrogen-free 

 medium. 



The same opinion has been held by various other investigators, and 

 is observed by all firms and institutions that distribute pure cultures 

 of the legume organism. Despite the fact that media low in nitrogen 

 have been employed, the results with pure cultures have not always 

 been satisfactory, and Kellerman (1912) has stated that the pure 

 cultures have not been as efficient as field soil.- It would seem, then, that 

 the conditions of isolation and cultivation of the legume organism must 

 influence the organism, or that possibly the soil conditions would exert 

 some influence on the efficiency of the organism to effect inoculation or 

 would have an influence on the plant to resist infection. 



SCOPE OF THE INVESTIGATION 



With these ideas in mind, the investigation herewith reported was 

 undertaken. It is concerned with the following: (l) Isolation and iden- 

 tification of the organism causing nodule development on the roots of 

 Canada field pea; (2) A study of the influence of various factors on nodule 



^ Laboratory of Plant Physiology, Contribution No. 15. 

 ^ Dates in parenthesis refer to bibliography, page 79. 

 ^ This is not the nitragin now on the market. 



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