Survival of Erwinia psidii in epiphytic, soil and eucalyptus leaf debris conditions

Abstract

AbstractErwinia psidii is an airborne bacterium that is the causal agent of eucalyptus bacterial blight in Brazil. However, there are no studies on the survival of the bacterial pathogen under epiphytic, soil and eucalyptus leaf debris conditions. We investigated the survival of E. psidii on the phylloplane and in leaf debris from two eucalyptus genotypes, and within eucalyptus forest soil. A rifampicin‐resistant mutant (CR01R) was obtained from the wild type by the gradient plate method and chosen for the study because it showed the same morphological, growth, pathogenic and aggressive properties as the parental strain. On the phylloplane of Eucalyptus urophylla × Eucalyptus globulus and E. saligna, the plant–pathogenic bacterium was recovered for up to 40 and 60 days, respectively. Under non‐sterile eucalyptus forest soil, E. psidii survived for 15 days post–soil infestation. In leaf debris from the eucalyptus genotypes, the bacterial pathogen was detected for up to 90 days in debris placed on the soil surface. However, under non‐sterile soil, 5 or 15 cm deep, the bacterium was detected for up to 45 and 60 days in leaf debris from E. saligna and E. urophylla × E. globulus, respectively. In this study, we showed that E. psidii can survive as an epiphyte or saprophyte in diseased leaves on the soil. However, the pathogen was a poor survivor in natural eucalyptus forest soil. The pathogen's survival period in leaf debris buried in the soil was drastically reduced. This information shows that the phylloplane or leaf debris is putative reservoirs for the bacterium and may serve as a primary inoculum source.