Soil and Rhizosphere Bacterial Diversity in Maize Agro- Ecosystem

Abstract

Management practices used in maize production have an impact on soil agro-ecosystems where different microbial communities coexist. Soil inhabiting bacteria are numerous and diverse, but we know very little about their ecological distribution. Here we analyzed the bacterial community diversity in the rhizosphere of two transgenic maize cultivars, in agricultural soil before sowing and in non-cultivated soil in an experimental site in the south region of Uruguay. We followed two culture-independent methods: DGGE (denaturing gradient gel electrophoresis) and 454-pyrosequencing of 16S rRNA gene amplicon. Through pyrosequencing, the three environments analyzed presented differences in terms of bacterial composition. However, no differences were found in the relative abundance of the ten most represented phyla in the rhizosphere of the two cultivars at different phenological stages. We found significant differences of Bacteroidetes, Gemmatimonadetes, Planctomycetes, Proteobacteria and Verrucomicrobia phyla when comparing agricultural and non-cultivated soils, as well as a significant enrichment of members of the phylum Gemmatimonadetes in all rhizosphere samples compared to soil. Through DGGE analysis we evidenced that maize rhizosphere bacterial communities changed at different phenological stages in both cultivars. We also provided baseline information about bacterial specific taxa within maize agro-ecosystem for further evaluation of possible rhizosphere bacterial community shifts of genetically modified maize cultivars under different management practices.

Metagenomic insights into the bacterial community structure and functional potentials in the rhizosphere soil of maize plants

“…Also, metagenomic analysis of wheat plants demonstrated that there was high bacterial diversity in the rhizosphere than in bulk soil (Velázquez-Sepúlveda et al 2012). In addition, during the initial stages of maize growth, several studies based mainly on selected rhizospheric isolates also reported higher bacterial diversity and stated that the rhizosphere of small plants is a more unpredictable ecosystem than the rhizosphere of mature plants (Rodriguez et al 2017). García-Salamanca et al (2013) observed in accordance with the assumption that the rhizosphere is more nutrientrich than bulk soil; the levels of activity of alkaline phosphatase, β-glucosidase and dehydrogenase enzymes from bacterial cells in the maize rhizosphere were higher than the same enzymatic activity tested in bulk soil.…”