Azospirillum brasilense Az39 inoculation effect on maize rhizosphere microbiome composition

CONIGLIO ANAHÍ; MOLINA, ROMINA; LARAMA GIOVANNI; MORA VERONICA; TORRES DANIELA; MARIN ANELIS; AVILA IGNACION; DE SOUZA, EMANUEL; CASSAN, FABRICIO

Otro; Relar PGPR; 2021

Azospirillum genus is used in agriculture bio-inoculants production for non-legumes inoculation and co-inoculation of legumes. Despite the fact inoculation with beneficial bacteria modifies the microbial communities associated with plants, few reports are available describing the effects of Azospirillum genus on the inoculated plant microbiome to date. A. brasilense Az39 is the preferred strain for maize inoculation in Argentina. In order to determine whether the A. brasilense Az39 inoculation modifies the bacterial microbiome associated with maize rhizosphere, a sequence analysis of the 16S rRNA gene was performed under controlled experimental conditions. Rhizosphere metagenomic DNA was obtained from plants inoculated and not inoculated with A. brasilense Az39 and bulk soil was used as a reference treatment. Biodiversity and microbial composition were analysed, a co-occurrence network was built and a FAPROTAX analysis was performed to predict metabolic functions based on the abundance of 16s rRNA sequences. Results showed that Azospirillum was the most abundant genus in inoculated plats rhizosphere. Regarding alpha diversity, only a significant difference was observed for the Pielou index. Beta diversity showed a defined structure for each rhizosphere communities, in comparison to the communities of non-rhizospheric soils. According to the LEfSe index, the three most abundant genera associated with Az39 inoculation were Burkholderia, Massilia and Sphingobium. Additionally, an increase in the relative abundance of some members of the Rhizobiales order was observed in inoculated plants. The co-occurrence networks showed a positive interaction between Azospirillum and Pseudomonas, and a negative correlation with Hyphomicrobium. FAPROTAX analysis showed some functions related to chemoheterotrophy, phototrophy and the nitrogen cycle. In conclusion, our results confirm that Azospirillum is able to colonizing the maize rhizosphere after inoculation and could induces an increase in relative abundance of some beneficial bacterial genera, also commonly used as biofertilizers in agriculture.