Identification of Bacteria for Biological Control of Botrytis cinerea on Petunia Using a Petal Disk Assay. Ann B. Gould, Department of Plant Pathology, Rutgers University, New Brunswick, NJ 08903. Donald Y. Kobayashi, and Marshall S. Bergen, Department of Plant Pathology, Rutgers University, New Brunswick, NJ 08903. Plant Dis. 80:1029-1033. Accepted for publication 31 May 1996. Copyright 1996 The American Phytopathological Society. DOI: 10.1094/PD-80-1029.

A total of 172 bacterial strains recovered from the surface of petunia leaves and flowers was evaluated for the ability to suppress Botrytis blight of petunia using a rapid, small-scale petal disk assay. Twenty-four strains were identified that consistently suppressed Botrytis cinerea sporulation by 100% on petal disks. Twenty-three of these strains were identified as fluorescent pseudomonads. One strain, Pseudomonas fluorescens PB92B10E, was tested for the suppression of Botrytis blight at the whole plant level. This bacterium reduced disease incidence by an average of 77% on whole flowers inoculated with B. cinerea conidia in seven different trials. Populations of a rifampicin-resistant mutant of PB92B10E increased by 104 g-1 of tissue (fresh weight) over a 7-day period on whole, nonsterile flowers. The isolation of P. fluorescens PB92B10E demonstrates the utility of the petal disk assay for the development of potential antagonists for management of greenhouse crop diseases.