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Absence of a Common Antigen Relationship Between Corynebacterium insidiosum and Medicago sativa as a Factor in Disease Development. R. B. Carroll, Graduate Assistant, Department of Plant Pathology, The Pennsylvania State University, University Park 16802, Present address of the senior author: Plant Science Department, University of Delaware, Newark, Delaware 19711; F. L. Lukezic(2), and Roslyn G. Levine(3). (2)(3)Associate Professor, and Research Assistant, respectively, Department of Plant Pathology, The Pennsylvania State University, University Park 16802. Phytopathology 62:1351-1360. Accepted for publication 31 May 1972. DOI: 10.1094/Phyto-62-1351.

No precipitin bands were formed in gel-diffusion tests comparing antigens and antisera from a resistant and susceptible alfalfa host and virulent and avirulent isolates of Corynebacterium insidiosum. Precipitin bands were formed between the homologous combinations included in the same tests and between: the two host cultivars; root and leaf antigens of the two cultivars; and the avirulent and virulent bacterial isolates. Serological differences were not detected when the antigens obtained from gnotobiotically and greenhouse-grown alfalfa were compared in gel-diffusion tests. Antigens obtained from crude host tissue extracts did not react with bacterial antisera, further demonstrating the lack of common antigens between the host and pathogen. No precipitin pattern shifts occurred when antigens from infiltrated and control leaves of a resistant and a susceptible cultivar were compared against host and bacterial antisera. The media and manner in which the pathogen was grown, prior to antigen preparation, had a pronounced effect on serological results obtained.