A NASTURTIUM WILT CAUSED BY BACTERIUM 

 SOIvANACEARUM 



By Mary K. Bryan, 



Scientific Assistant, Laboratory of Plant Pathology, 



Bureau of Plant Industry 



INTRODUCTION 



On July 21, 1914, some badly wilted nasturtiums {Tropaeolum majus) 

 were received from Dr. John Arthur Luetscher of Baltimore, Md., who 

 wrote concerning them : 



Seven years ago I raised a fine lot of nasturtiums, but in the last six years I have 

 hardly been able to get a blossom, although the plants have been in the same soil 

 and several times in the same plat. The leaves wither and the plant dies. 



The plants, which were of the dwarf variety and much-branched, were 

 poorly developed, and the leaves mostly wilted, yellowed, or dead 

 (Pi. LXIII). The stems had a peculiar translucent or water-soaked 

 appearance, allowing the vascular bundles to show as darkened streaks 

 beneath the unbroken epidermis. When the stem was cut across, there 

 oozed from these bundles a grayish white viscid slime which became 

 brown on standing. 



ISOLATION OF THE ORGANISM 



On cross-sectioning such stems the vessels were found to be clogged 

 with bacteria, often every bundle being entirely occluded. Agar-poured 

 plates gave pure cultures of a white bacterial organism. Inoculations 

 made from colonies on these plates into nasturtium stems produced 

 signs of the disease — i. e., wilted leaves and water-soaked stems — within 

 seven days (PI. LXIV). From one of these stems the organism was 

 reisolated on agar-poured plates and again produced typical wilt within 

 four days when inoculated into healthy young nasturtiums, using sub- 

 cultures from single colonies. 



NATURE OF THE ORGANISM 



Cultural work was then begun, but it was not until the growth on 

 potato cylinders began to blacken that the identity of the organism 

 with Bacterium solanacearum ^ was suspected. To test this hypothesis, 

 inoculations were at once made into tomatoes (Lycopersicon esculentum) , 

 the only available plants being rather old. The result was the formation 

 of numerous adventive roots in the vicinity of the needle pricks and the 

 slow wilt of a few leaflets. Vessels were browned and filled with these 



' Originally described by Erwin F. Smith as Bacillus solanacearum under the supposition that it was 

 peritrichiate, but afterwards transferred by him to the genus Bacterium, in accordance with his system 

 of nomenclature in his Bacteria in Relation to Plant Diseases, v. i, p. 171. Washington, D. C, 1905. 

 (Carnegie Inst. Wash. Pub. 27.) 



Journal of Agricultural Research, Vol. IV, No. s 



Dept. of A^culture, Washington, D. C. Aug. 16, 1915 



G-S3 



(451) 



