Niche-dependent microbial assembly in salt-tolerant tall fescue and its contribution to plant biomass

Tall fescue (Festuca arundinacea Schreb.) is promising for biogas production in cold climate zones and displays good performance and high biomass under moderate to severe salt stress. The plant microbiome is crucial for enhancing plant growth and boosting crop yield under salt stress. To determine the variations of microbiome composition and abundance in different plant compartments with salt-tolerant tall fescue cultivars under salt stress, this study performed 16S ribosomal RNA amplicon and internal transcribed spacer (ITS) sequencing. Moreover, the study investigated the effect of enriched bacteria on tall fescue growth and salt tolerance. The aboveground and belowground compartments shaped distinct and overlapping microbial communities, as evidenced by the fact that Proteobacteria and Ascomycota displayed various preferences in inhabiting each compartment. Salt stress drove significant changes in microbiome composition in different compartments. Interestingly, the abundance and diversity of bacteria varied more significantly than those of fungi in response to salt stress. Microbes may enhance the carbon fixation pathways in prokaryotes and flagellar assembly functions to improve the salinity tolerance of tall fescue. Moreover, the inoculation experiment revealed that Halomonas lutescens could promote plant salt tolerance and biomass accumulation. Taken together, this research presents clear insight regarding the dynamics of plant microbiome recruitment in different tall fescue compartments under salt stress and highlights the role of the microbes in regulating plant salt tolerance, thus offering huge potential for increasing the resilience of crop and bioenergy production in agriculture and industry to salt stress.