Seed Transmission of Clavibacter michiganense subsp. nebraskense in Corn. J. A. Biddle, Department of Plant Pathology and Seed Science Center, Iowa State University, Ames 50011. D. C. McGee, and E. J. Braun. Department of Plant Pathology and Seed Science Center, Iowa State University, Ames 50011. Plant Dis. 74:908-911. Accepted for publication 28 April 1990. Copyright 1990 The American Phytopathological Society. DOI: 10.1094/PD-74-0908.

Clavibacter michiganense subsp. nebraskense, the Goss’s wilt pathogen, was detected in seeds, ear shanks, and stalks of a susceptible corn inbred, A632Ht, after leaves were inoculated in the field one, two, or three times with a rifampicin-tolerant strain of C. m. subsp. nebraskense. Pathogen populations tended to increase in all plant parts with increasing numbers of inoculations. In a second year of the study, in which the same inbred was inoculated three times, internal populations of the bacterium in seedlots were similar to those in the previous year, and the percentage of seeds infected ranged from 17.1 to 30.7. Internal populations of the pathogen and the percentage of seeds with these populations were not affected by either moisture content at harvest (38% or 25%) or by drying at 35 C. Transmission of the pathogen into seedlings did not occur when nine 1,000-seed samples from infested seed lots were planted in sterile soil in the greenhouse or when three 1,000-seed samples were planted in the field. The pathogen was transmitted to seedlings at rates of 0.1–0.4% from seeds that had been inoculated with C. m. subsp. nebraskense by vacuum infiltration.