Impact of Azospirillum brasilense Az39 inoculation on the maize microbiome

CONIGLIO, ANAHÍ; LARAMA, GIOVANNI; MOLINA ROMINA; MORA, M VERONICA; TORRES DANIELA; MARIN, ANELIS; AVILA, ANDRES; DE SOUZA, EMANUEL; CASSÁN F.

Otro; IV REUNIÓN CONJUNTA DE SOCIEDADES DE BIOLOGÍA DE LA REPÚBLICA ARGENTINA; 2020

Azospirillum is one of the most used genera for agriculture worldwide. Inoculation with many plant growth-promoting rhizobacteria (PGPR)modifies the microbial communities associated with plants, but few reports are available for Azospirillum. In order to understand if the A. brasilenseAz39 inoculation modifies the bacterial populations associated with maize rhizosphere, we performed a metagenomics analysis under experimentalcontrolled conditions. For this purpose, maize seeds were pre-germinated for 7 days and transplanted to pots containing soil samples obtained from ageoreferenced agricultural region of the Córdoba Province (Argentina). The seedlings were inoculated at root level with 100 L of 1×108cfu/mL ofA. brasilense Az39 (inoculated rhizosphere). An equivalent volume of sterile distilled water was added to non-inoculated seedlings (non-inoculatedrhizosphere) and non-inoculated soil treated with an equivalent volume of sterile water (bulk soil) were used as control treatments. After 14 daysincubation, the whole DNA was extracted from the rhizosphere, and the V4 region of the bacterial 16S rRNA gene was amplified and sequencedusing the Illumina MiSeq platform. The genus relative abundances were evaluated and both alpha and beta diversity were assessed. The microbialdifferences were explored using LEfSe and IndicSpecies algorithms and a co-occurrence network analysis was performed. Results showed thatAzospirillum was the most abundant genus in inoculated samples which confirms its ability to colonize the maize rhizosphere. A significantdifference was observed for alpha diversity according to the Pielou index. No differences in the beta diversity between Az39 inoculated and noninoculated rhizospheres were observed. However, these communities maintained a differential structure in comparison with the bulk soil. Accordingto LEfSe index, the four most abundant genera associated with Az39 were Burkholderia, Massilia, Sphingobium and Cupriavidus, while Azospirillumand Pseudomonas were the most abundant genera according to IndicSpecies. An increase in relative abundance of some members of the Rhizobalesorder was observed by inoculation of Az39 in the maize rhizosphere. Finally, the co-occurrence network showed a positive interaction betweenAzospirillum and Pseudomonas genus. The ability of Azospirillum to colonize the maize rhizosphere induced changes in relative abundance of somebacterial genera in the rhizosphere and such changes could involve new interactions between these recruited microorganisms in the microbiome andtogether with some differential effects on plants.