Bidirectional colonization and biofilm formation by Erwinia psidii in eucalypt plants

Abstract

Dieback and wilt caused by Erwinia psidii is an emerging disease that has been causing considerable damage in eucalypt plantations. Because it is a recently emerged disease, several aspects of the bacterial interaction with its host still remain to be elucidated. In this work, we studied the E. psidii colonization and biofilm formation in eucalypt tissues by specific detection using PCR and scanning electron microscopy (SEM). The results indicate that the bacterium is able to translocate in stem tissue mainly acropetally, although movement in the basipetal direction was also observed to a lesser extent, always through the xylem. No colonization of phloem tissues was observed. In addition to colonizing the xylem, E. psidii colonized the parenchymatous tissue. The bacterium formed cell aggregates enveloped by fibrillar material that evolved into complex, well‐structured biofilms in stem and leaf tissues. In contrast, no biofilm formation was observed on abiotic surfaces. These observations suggest that biofilm formation plays an important role in the elicitation of dieback and wilt symptoms caused by E. psidii on eucalypt plants. This study not only shows ultrastructural aspects of the E. psidii communities but also tissue damage in eucalypt plants that was associated with the presence of bacterial aggregates and formation of tyloses.

Validation and use of a qPCR protocol to quantify the spread of Ralstonia solanacearum in susceptible and resistant eucalypt plants

“…As was demonstrated histologically in a previous work for Erwinia psidii in eucalypt (Caires et al, 2020), our work showed that R . solanacearum translocates acropetally and basipetally in both susceptible and resistant eucalypt clones.…”

A standard area diagram set for assessing severity of eucalyptus bacterial blight caused by Erwinia psidii

“…Production losses can reach 30% in forests planted with susceptible genotypes. The disease is caused by the plant-pathogenic bacterium Erwinia psidii (RODRIGUES NETO et al, 1983), which colonizes the xylem vessels and parenchymal intercellular spaces (CHAI et al, 2017;CAIRES et al, 2020). Besides affecting eucalyptus, the pathogen can cause serious damage to guava and papaya crops in tropical and subtropical conditions (RODRIGUES NETO et al, 1983;COUTINHO et al, 2011;CHAI et al, 2017).…”