Mycelia Migratory Bacteria in Compost and Compost-Amended Rhizosphere Soil in a Table Grape Orchard

PurposeIt is recognized that compost application incorporates a high diversity of microorganisms in soils, promoting the sustainable agriculture. However, bacterial-fungal interactions (BFI) in compost application remain insufficiently explored. Here, we determined and compared the composition of bacterial community in samples of commercial compost (C), compost-amended rhizosphere soil (RSC) and bulk soil (BS) from a table grape orchard in central Chile. Then, collected samples were used as sources for isolation of fungal strains and determine their associated mycelia migratory bacteria. MethodsBacterial community composition was determined by DNA metabarcoding analysis using 16 S rRNA as target gene in C, RSC and BS samples. Fungal highway column system (FHCS) were used to obtain 18 fungal isolates from C and RSC samples, and mycelia migratory bacterial community was further analyzed using 16 S rRNA gene metabarcoding analysis. ResultsRichness, diversity and connectivity of bacteria were higher in RSC and BS samples compared to C samples, with members of Actinobacteria (Actinomycetota; 11-46%) and Proteobacteria (Pseudomonadota; 22-38%) as the most abundant phyla. Conversely, Firmicutes (Bacillota) exclusively dominate (> 90%) the mycelia of 9 out of 18 fungal isolates, while Proteobacteria and Actinobacteria were dominants (> 90%) in 2 and 1 out of 18 fungal strains. ConclusionThis study demonstrated that a high diversity of bacteria are selected and effectively dispersed by fungi contained in commercial compost and compost-amended rhizosphere of the table grape orchard. A bacterial selectivity by isolated fungal strains was also evidenced but the specific BFI involved is still unclear and need to be addressed in further studies.