Effective partnerships
Root tip inoculation with Pseudomonas fluorescens strainPf SS101 resulted in a significant increase in shoot biomass in both Arabidopsis and Artemisia (63.1% ± 4.7 and 38.7% ± 6.3, respectively) (Figure 1b ). Similarly, root tip inoculation withParaburkholderia graminis strain PHS1 (Pbg ) resulted in significant increases in shoot biomass of both Artemisia and Broccoli (470.4% ± 21.3 and 54.1% ± 11.9, respectively). With a biomass increase of almost 5-fold relative to the untreated control plants,Pbg -Artemisia was considered as the most effective partnership. Likewise, the effect of the rhizobacterial strains on root biomass and architecture was highly species-specific (Figures 1a, 1c and Supplementary material, Figure S1 ). Pbgresulted in significant increases in root biomass in both Artemisia and Broccoli (773.9% (± 28.2) and 258.8% (± 50.1), respectively) (Figure 1c ). Inoculation of MB induced significant increase in shoot biomass only in Arabidopsis. The best-performing partnerships were characterized by an early and sustained growth promotion (Figures 1d-f ). For example, Pbg -Artemisia showed a significant increase in shoot fresh biomass as early as 5 dpi, while growth promotion in the combination of Pf SS101- Artemisia was only apparent after 13 dpi (Figure 1e ). Pbg- Broccoli showed a significant and sustained plant growth promotion at 7 dpi compared to the control plants (Figure 2f ). In Arabidopsis, only Pf SS101 and MB induced a significant increase in shoot biomass (Figure 1d ).