B. r. I.— 660. 



THE RELATION OF CROWN-GALL TO 

 LEGUME INOCULATION. 



INTRODUCTION. 



The relative merits of the inoculation of legumes by the pure- 

 culture method and by the scattering, of soil taken from old well- 

 inoculated fields have been widely discussed, and both methods have 

 been recommended by this Bureau. In case old soil is used, the fields 

 from which it is secured should be free from objectionable weeds and 

 insect pests and free from plant diseases. 



From time to time specimens of supposedly well-inoculated plants 

 of alfalfa, crimson clover, and alsike clover have been forwarded to 

 the Laboratory of Soil-Bacteriology Investigations with the explana- 

 tion that although nodules were produced in abundance the legumi- 

 nous crop was not satisfactory. In these cases the appearance of 

 the nodules was abnormal and the bacteria isolated from them, al- 

 though resembling the nodule-forming organism, did not have the 

 power of fixing nitrogen in culture solutions, and as a tentative 

 explanation it was suggested ^ that this was but an extreme case of 

 pleomorphism of Pseud omonas radlckola, which could be of no sym- 

 biotic advantage to the leguminous host. 



During 1909 the organism occurring in the abnormal nodules of 

 alfalfa was studied more extensively, and it was decided that this 

 organism represented a new, although not a destructive, disease of 

 al&lfa. Through the courtesy of Drs. Smith and Townsend a com- 

 parative study was made of material furnished by the Laboratory of 

 Soil-Bacteriology Investigations, which showed that the bacteria 

 causing the abnormal nodules upon alfalfa were practically identical 

 with those causing the crown-gall of orchard trees. 



In a recent bulletin - Smith, Brown, and Townsend have reported 

 extensive studies upon the crown-gall of fruit trees, proving con- 



1 Moore, George T. Soil Inoculation for Legumes; with Reports upon tho Successful 

 Use of Artificial Cultures by Practical Farmers. Bulletin 71, Bureau of Plant Industry, 

 1905. 



2 Smith. Erwin F., Brown. Nellie A., and Townsend, C. 0. Crown-Hciil ..f Plat.ts ; Its 

 Cause and Remedy. Bulletin 213, Bureau of Plant Industry, 1911. 



[Cir. 76] _ 



