Tomato genotype and Azospirillum inoculation modulate the changes in bacterial communities associated with roots and leaves

Abstract

To evaluate the effect of plant variety and Azospirillum brasilense inoculation on the microbial communities colonizing roots and leaves of tomato (Lycopersicon esculentum Mill.) plants. Seeds of cherry and fresh-market tomato were inoculated with A. brasilense BNM65. Sixty days after planting, plants were harvested and the microbial communities of the rhizoplane and phyllosphere were analysed by community-level physiological profiles (CLPP) using BIOLOG EcoPlates and denaturing gradient gel electrophoresis (DGGE) of PCR-amplified 16S rRNA genes. Differences on the rhizoplane and phyllosphere bacterial communities between the two tomato types were detected by principal component analysis of the CLPP; DGGE fingerprints also showed differences at the phyllosphere level. Fresh-market tomato had a more complex phyllosphere bacterial community than cherry tomato, as determined by DGGE profiles. Physiological and genetic changes on phyllosphere and rhizoplane bacterial communities by Azospirillum seed inoculation were evident only on cherry tomato. Tomato genotype affects the response of native bacterial communities associated with the roots and leaves to A. brasilense seed inoculation. The successful implementation of Azospirillum inoculation requires not only the consideration of the interactions between A. brasilense strains and plant genotypes, but also the plant-associated microflora.