VIEW ARTICLE

Physiology and Biochemistry

Comparison of Different Immunogen Preparations for Serological Identification of Xanthomonas campestris pv. campestris. N. Thaveechai, Graduate student, Department of Plant, Soil and Entomological Sciences, University of Idaho, Moscow 83843; N. W. Schaad, professor, Department of Plant, Soil and Entomological Sciences, University of Idaho, Moscow 83843. Phytopathology 74:1065-1070. Accepted for publication 20 December 1983. Copyright 1984 The American Phytopathological Society. DOI: 10.1094/Phyto-74-1065.

Four immunogens- formaldehyde fixed cells, glutaraldehyde fixed cells, trichloroacetic acid extracts, and ribosomal extracts- were compared for identification of Xanthomonas campestris pv. campestris (XC). In Ouchterlony double diffusion (ODD) tests, antiserum (AS) to each of the immunogens resulted in a single major band and one to three minor bands of precipitin when reacted against homologous cell extracts. A reaction of complete fusion (identity) occurred between the major band of precipitin of the four immunogens. However, the major precipitin was considerably sharper and stronger in the AS to ribosomes. By means of AS to ribosomes and the major precipitin, 25 strains of XC were typed into four serovars. Thirty-two other bacteria, including 16 strains of five other pathovars of XC, 12 strains of five other genera, and four unidentified bacteria from crucifer seeds, were tested by ODD with AS to the four serovars. Three strains of X. vesicatoria and one strain of X. translucens cross-reacted; all other bacteria failed to react. Two to four immunogens were identified in immunoelectrophoresis. The major band of precipitin was identified as a neutral immunogen. In immunofluorescence (IF) tests, few differences were observed among the four immunogens. The greatest specificity was found with AS to glutaraldehyde and formaldehyde fixed cells. None of the immunogens, however, was specific enough in IF to differentiate XC from other xanthomonads.