Growth stimulation of barley and biocontrol effect on plant pathogenic fungi by a Cellulosimicrobium sp. strain isolated from salt-affected rhizosphere soil in northwestern Algeria

• Cellulosimicrobium sp. S16 stimulated barley seedling growth.
• Strain S16 efficiently inhibited the growth of the studied plant pathogenic fungi.
• Strain S16 harbored several plant growth promoting traits (e.g., IAA-production).
• Strain S16 exhibited different enzyme activities beneficial for soil fertility.
• Other isolates from the genus Streptomyces also showed PGP and other beneficial effects.

The plant growth promoting effect of bacterial isolates from salt-affected agricultural rhizospheric soil from Bejaia, Algeria, on barley seedlings as well as biological control abilities of these isolates against phytopathogenic fungi were determined. Four isolates stimulated significantly germination and growth of barley seedlings in an axenic test system and in soil pots. Isolate S16 (Cellulosimicrobium sp.) stimulated the growth of barley seedlings by 185% (stem height of 13.0 ± 0.11 cm) over non-inoculated control seedlings (7.0 ± 0.12 cm). Cellulosimicrobium sp. S16 was found also superior in mycelial growth inhibition assays against the plant pathogenic fungi Botrytis cinerea, Fusarium oxysporum and Verticillium dahliae. Furthermore, several plant growth promoting traits (production of indole acetic acid, inorganic phosphate solubilization, siderophore production) and production of enzymes beneficial for soil fertility (protease, chitinase, amylase and urease) were identified. However, no evidence for nitrogen fixation was found by testing acetylene reduction and the presence of nif-genes. Based on comparative sequence analysis of almost full length 16S-rRNA coding gene fragments, Cellulosimicrobium sp. S16 exhibits the highest similarity of 99.7% to Cellulosimicrobium cellulans (accession number AY665978). Cellulosimicrobium sp. S16 could be a successful candidate for the application as a plant growth promoting inoculant.