972 MICROBIAL DISEASES OF PLANTS 



proliferation in the presence of dividing cells. The hypertrophy of 

 the plant cell is associated with hypertrophy of its nucleus and it is 

 evident that the growth and increase of the parasite is favored by 

 the reaction which its presence excites. 



TUBERCULOSIS or SUGAR-BEET 

 Pseudomonas beticola Smith 



HISTORY. This new disease of the sugar-beet, resembling somewhat 

 crown gall on the surface, but distinct from it, was first observed in 

 the autumn of 1910 on beets from Colorado and Kansas. 



SYMPTOMS. Affected beets bear numerous wart-like outgrowths or 

 tubercles on the upper portion of the root. On section these show 

 small, water-soaked, brownish areas with more or less necrotic tissue 

 in their interiors; such areas may develop small central cavities, and 

 the softening may extend into the ungalled part of the beet; the dis- 

 eased parts appear mucilaginous and stringy when touched, and under 

 the microscope this broken-down tissue is found to be swarming with 

 bacteria. 



CAUSAL ORGANISM. According to Smith* Pseudomonas beticola, n. sp., is a 

 motile rod with rounded ends, single or in pairs, chains or clumps; measures 0.6 

 to 0.8 by 1.5 to 2.o/i; flagella polar; no spores observed; capsule present; liquefies 

 gelatin, but not blood serum; grows in beef bouillon containing 9 per cent NaCl; 

 uniform clouding and copious pellicle which falls easily in bouillon; thermal death- 

 point 51; grows at 37 but best at 20; grows slowly at i; produces a yellow 

 rim and pellicle in plain milk which is slowly coagulated; whey separates slowly; 

 litmus mUk is blued and later reduced; grows readily in Uschinsky's solution, 

 viscid; no growth in Cohn's solution; moderate growth on potato; does not 

 produce gas from dextrose, lactose, saccharose, maltose, mannite or glycerin; agar 

 colonies, circular, smooth or wrinkled; indol is produced; grows in bouillon over 

 chloroform; resists drying; stains by Gram; is yellow or becomes yellow on all 

 ordinary media. 



* Smith, Erwin P., "Crown Gall of Plants: Its Cause and Remedy." Bull. 213, Bur. Plant 

 Ind., U. S. Dept., Agr., p. 194, 1911. 



