Context-dependent effects of various synthetic communities on the ecological dynamics of sugarcane rhizosphere

The plant rhizosphere harbors diverse microbes that play critical roles in plant health and productivity. Introducing beneficial microbes as inoculants to modify the rhizosphere community represents a promising approach to sustainable agriculture. Despite this potential, the ecological dynamics governing autochthonous community responses to various synthetic communities (SynComs) are poorly understood. This study assessed the sugarcane rhizosphere community and plant growth following inoculation with three SynComs, namely MetG2, OG10, and Sugarcane2, along with an NPK fertilizer treatment and water as a control. Phenotypic observations of the plants indicated that all SynComs enhanced plant height and number of new tillers compared to the control, showing performance levels comparable to the fertilizer. High-throughput 16S rRNA amplicon sequencing unveiled inoculant- and time-dependent alterations in community diversity, composition, and ecologically functional capacities of the sugarcane rhizosphere. Temporal enrichment patterns were observed in taxonomy at both phylum and genus levels. Succession analysis identified distinct amplicon sequence variants (ASVs) induced by different SynComs, with MetG2 having the lowest number of unique declining ASVs, indicating greater compatibility with the existing microbial community. Fertilizer promoted specialist taxa at the early stage, while control, OG10, and MetG2 revealed an opposing trend. A null model analysis indicated strong initial effects of inoculants on deterministic assembly, diminishing over time, particularly in OG10. Taken together, our findings underscored the context-dependent nature of SynCom's effects on rhizosphere community dynamics, shedding light on the potential for tailored microbial inoculation strategies to shape desired ecological outcomes.