Shifts in the structure and composition of root-associated bacterial communities caused by Ceratocystis fimbriata infection in eucalyptus

Abstract

Ceratocystis fimbriata is the causal agent of Ceratocystis wilt in eucalypt plantations, resulting in lower volumetric growth, lower pulp yields and reduced timber. Therefore, the first hypothesis is these changes also could affect root-associated bacterial communities; and second hypothesis is that some bacteria associated with eucalyptus roots may act as a natural barrier against C. fimbriata. The structure and composition of bacterial communities associated to roots of eucalyptus plants presenting four levels of infection by C. fimbriata were evaluated. The abundance of rhizoplane community was higher than in endorhizosphere. On rhizoplane the abundance was higher in healthy than the infected plants, suggesting that these communities respond differentially to the C. fimbriata infection. C. fimbriata infection has effect on the endophytic bacterial community. The Pseudomonas fluorescens, P veronii, and Rahnella aquatilis were isolated only from roots of healthy plants. It was confirmed that R. aquatilis effectively controls C. fimbriata in vitro, strongly suggesting a negative association between the abundance of these bacterial species and the presence of C. fimbriata infection. In summary, data clearly suggest that sequential dynamics in shifting bacterial communities could be taken into account to increase understanding of the underlying mechanisms of C. fimbriata root infection.

Keywords

• 16S rRNA
• DGGE
• Eucalyptus disease
• Plant-bacteria-phytopathogen interaction