Viscosity Test for Preliminary Identification of Strains of Xanthomonas campestris. Luellen Pierce, Department of Plant Pathology, University of California, Berkeley 94720. M. N. Schroth, and A. H. McCain. Department of Plant Pathology, University of California, Berkeley 94720. Plant Dis. 74:646-647. Accepted for publication 31 January 1990. Copyright 1990 The American Phytopathological Society. DOI: 10.1094/PD-74-0646.

A diagnostic test based on the viscosity of suspensions prepared from 6- to 7-day-old cultures differentiated 16 of 17 pathovars of Xanthomonas campestris from miscellaneous yellow bacteria. The viscous suspensions of xanthomonads (viscosity presumed to be caused by xanthan gums) required ?26 sec for 0.9 ml to flow through a 1-ml Pyrex pipet, vs. 5.6 sec or less for other yellow bacteria.