Metataxonomics of 16S rRNA gene of maize bulk and rhizospheric soil samples with seed bacterization with Azospirillum brasilense Ab-V5 in a dilution-to-extinction of native microbial diversity

The beneficial plant-microbes association has been widely explored with the purpose of understanding the mechanisms involved in this interaction, in order to develop bioinoculants for agriculture aiming at sustainability and reduction of chemical inputs use. Plant growth promoting bacteria (PGPBs) have been reported as an interesting alternative to mineral fertilizers for a range of crops. The genus Azospirillum has shown potential in plant growth promotion for maize. However, the lack of holistic comprehension about PGPBs-plant-native soil microbiota can lead to inconsistency of results in field conditions. Recent ecological theories revealed that plant microbiomes are organized as microbial hubs with keystone species and helpers. The objective of this work is to characterize the microbial community associated with a commercial maize genotype (30A37PW) under influence of the potential keystone PGPB A. brasilense Ab-v5 to support the original development of a synthetic minimum microbiome including this strain as keystone for plant growth promotion. Aiming to understand the PGPB-plant-microbiome system, we conducted a greenhouse experiment in which the synergistic effect of Ab-V5 and soil native microbial community were evaluated through soil and rhizosphere metataxonomics, metagenomics and plant phenomics. Our results revealed that maize seed bacterization with the PGPB Ab-V5 promotes plant growth. This effect is boosted by the interaction with specific microbial groups present in the soil native community. The strain Ab-V5 persists in the maize rhizosphere until 25 days after sowing. In order to understand which microbial groups are important during the interaction Ab-V5-plant-native soil microbial community, 16S rDNA metataxonomics and metagenomics analysis will be conducted in maize soil and rhizosphere samples. This unprecedented omics approach for the holistic view of the complex system composed by inoculant-plant-microbiota and data integration will allow the development of new strategies for optimization of plant biostimulants recommendation with enhanced efficiency for establishment in the field.