Biochemical and pathogenic differences between Kenyan and Brazilian isolates of Pseudomonas syringae pv. garcae

Abstract

Isolates of Pseudomonas syringae pv. garcae from Kenya and Brazil differed in pathogenic and biochemical characters. In inoculations on Coffea arabica var. SL28 from Kenya, only the Kenyan isolates were virulent. The Kenyan isolates were not bacteriocin producers while the Brazil on isolates were active producers comparable to P. s. syringae from lilac (Syringa vulgaris). Pigment production separated the two types of P.s. garcae isolates distinctly. The Kenyan isolates produced the UV fluorescent yellow-green siderophore while the Brazilian isolates produced a nonfluorescent brown diffusible pigment on King's B medium. API-20NE diagnostic kits were largely ineffective in distinguishing between biochemical reactions of P.s. garcae isolates from Kenya and Brazil or between these and P.s. syringae. Syringomycin activity on lemon and Geotrichum candidum distinguished P. s. syringae from P.s. carcae isolates. It is concluded that P.s. garcae (as represented by the seven cultures from the National Collection of Plant Pathogenic Bacteria, Harpenden, UK) exists in at least two strains, the Kenyan isolates comprising one strain while the Brazilian isolates comprise one or more distinct strains.