Avirulence Gene avrPphC from Pseudomonas syringae pv. phaseolicola 3121: A Plasmid-borne Homologue of awC Closely Linked to an avrD Allele. Irem Yucel. Department of Plant Pathology, University of California, Riverside 92521 U.S.A. David Slaymaker (1), Carol Boyd (1), Jesus Murillo (1), R. I. Buzzell (2), and Noel T. Keen (1). (1) Department of Plant Pathology, University of California, Riverside 92521 U.S.A., and (2) Research Station, Harrow, Ontario, Canada. MPMI 7:677-679. Accepted 20 June 1994. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1994.

Cosmid clone pPsp0l from race 1 Pseudomonas syringae pv; phaseolicola isolate 3121 conferred a unique pattern of soybean cultivar reactions when expressed in P. s. pv. glycinea R4. The avirulence phenotype was shown to result from the presence in clone pPsp0l of an avrD allele as well as an additional avirulence gene located approximately 5-kb upstream. The new gene, called avrPphC, shows high identity to and is phenotypically identical to avrC, previously cloned from P. s. pv. glycinea race 0. avrD and avrPphC occur on an approximately 120-kb indigenous plasmid in P. s. pv. phaseolicola 3121. Although commonly observed in Xanthomonas campestris, this is the first noted occurrence of multiple avirulence genes on a single plasmid in Pseudomonas syringae. Unlike avrD, however, avrPphC does not appear to occur widely in pathovars of Pseudomonas syringae.