Phylloplane as a potential Erwinia psidii inoculum reservoir
摘要
Erwinia psidii is an airborne and waterborne bacterium that causes eucalyptus bacterial blight, a destructive disease occurring in eucalyptus forests in Brazil. To design assertive and efficient control strategies to reduce or eliminate the incidence of the disease, it is necessary to understand the ability of the plant-pathogenic bacterium to survive in phylloplane conditions. We investigated the survival of E. psidii on the phylloplane of Eucalyptus urophylla (SUZBA1175), E. urophylla (SUZBA1922), E. grandis × E. urophylla (FA6825), Lantana camara, Brachiaria decumbens, Conyza bonariensis, Digitaria insularis, Psidium guajava, and Eugenia uniflora plants. An inoculum of 107 CFU of rifampicin-resistant E. psidii was sprayed onto the leaves of these plants, and the number of viable cells was counted every 7 days. For each plant species, three replicates were used, with each replicate consisting of three plants. The experiment was repeated twice for each group of plants. The plants were kept in a greenhouse under semi-controlled temperature and humidity conditions. On the phylloplane of eucalyptus genotypes, the survival of the bacterial pathogen varied between 35 and 56 days. On the phylloplane of E. uniflora and P. guajava, E. psidii was recovered for up to 77 and 85 days, respectively. Bacterial cells were recovered for up to 7 days on B. decumbens and D. insularis. On the other hand, on L. camara and C. bonariensis, the bacterium survived for up to 21 days. In this study, we showed that E. psidii can persist as an epiphyte on the leaf surface of eucalyptus genotypes, on plants from the same botanical family as eucalyptus, and on weeds. This brings us the important information that the phylloplane is a putative reservoir for E. psidii and can serve as a primary inoculum source for new infections or increase of bacterial blight in eucalyptus forests.