Under field conditions, onion seedlings in a nursery exhibiting typical soft rot in their root system and aerial parts vvere observed. The etiology of the disease was investigated and the disease was found to be induced by a bacterium. Obtained bacterial isolates were white pearl in color, non pigmented, able to grow in routine culture media and their cells were single, straight, regular rods. Phytopathogenicity of the isolates was confirmed by both hypersensitive test in leaves of non hots plants (coffee, pepper and tobacco) and host inoculation by several methods. Biochemical tests, staining methods and biological procedures lead to the conclusion that isolates under investigation belong to the genus Pseudomonas, non fluorescent group. Moreover, more specific tests indicated that isolates belong, from the taxonomic standpoint, to the patovar P. gladioli pv. alliicola. By the growing-on test was found the seed transmission of the pathogen, and the rate of seed transmission was about 9%. Detection of the bacterial pathogen in non germinated seeds was accomplished by the use of biological baites.