Indirect Immunofluorescent Staining for Detection and Identification of Xanthomonas campestris pv. phaseoli in Naturally Infected Bean Seed. Eileen M. Malin, Graduate Assistant, Department of Plant Science, University of Wyoming, Laramie 82071. Don A. Roth, Assistant Professor, Department of Plant Science, and E. Lee Belden, Professor, Department of Microbiology and Veterinary Medicine, University of Wyoming, Laramie 82071. Plant Dis. 67:645-647. Accepted for publication 22 November 1982. Copyright 1983 American Phytopathological Society. DOI: 10.1094/PD-67-645.

Indirect immunofluorescence (IF) was evaluated for detecting and identifying Xanthomonas campestris pv. phaseoli in pure and mixed culture and in Pinto and Navy bean seed. IF was specific for 24 X. c. pv. phaseoli isolates tested that were collected from diverse geographical locations. Strong positive cross-reacting fluorescence was not observed when antiserum was tested against numerous X. campestris pathovars as well as other pseudomonads and common bean seed bacteria. Cells of X. c. pv. phaseoli were detected on prepared slides in mixed bacterial populations containing as few as 250 colony-forming units (cfu) per milliliter of X. c. pv. phaseoli and 10⁸ cfu/ml of common bean seed bacteria. Cells of X. c. pv. phaseoli were detected in naturally infected bean seed lots with infection levels of 0.01% and in bean seed leachate to which 10² cfu/ml of X. c. pv. phaseoli were added . IF provides a reliable method for rapid screening of bean seed lots for X. c. pv. phaseoli although it is not viewed as the sole test for final determination of seed certification.