Occurrence of Pseudomonas syringae pv. garcae in coffee seeds

Abstract

Given the damage and losses caused by bacterial blight of coffee (Pseudomonas syringae pv. garcae) (PSG) in coffee (Coffea arabica) seedling nurseries and lack of knowledge of the origin of the initial inoculum, the goal of this study was to determine whether coffee seeds can contain viable inoculum and spread bacterial inoculum. Seeds from plants with symptoms of bacterial blight of coffee were immersed in sterilized saline solution, and the crude extract obtained was inoculated in leaves of coffee seedlings. Leaves of plants inoculated with seed extract from symptomatic plants had symptoms of bacterial blight similar to those on leaves inoculated with reference isolate PSG. Seedlings inoculated with seed extract from asymptomatic plants showed no symptoms. Symptomatic leaves were submitted to exudate tests, and the etiologic agent was isolated in culture medium. The isolates with colonies morphologically similar to reference isolate PSG were selected and tested for hypersensitive reaction (HR) and pathogenicity to coffee seedlings. The isolates positive for HR and pathogenic to coffee also showed biochemical and molecular patterns equal to those of reference isolate PSG by the rep-PCR technique using Box primer. Thus, coffee seeds from plants with symptoms of bacterial blight can contain viable inoculum of P. syringae pv. garcae.