Aydi Ben Abdallah Rania, Jabnoun-Khiareddine Hayfa, Nefzi Ahlem, Daami-Remadi Mejda, Stedel Catalina and Ppadopoulou Kalliope K
Eight endophytic bacterial strains (Bacillus spp., Stenotrophomonas maltophilia, and Pseudomonas geniculata) recovered from healthy cultivated tomato (Solanum lycopersicum L.) were screened for their plant growth-promoting potential on tomato plants challenged with Fusarium oxysporum f. sp. lycopersici (FOL) and for their in vitro and in vivo antifungal activity against FOL. S. maltophilia CT16 and Bacillus subtilis subsp. inaqosorum CT43 and their filtrates were the most efficient in controlling disease by 55-87.5% and in improving growth parameters in inoculated tomato plants by 8.4-46.8%. Pathogen sporulation was inhibited and FOL mycelial growth was reduced using whole-cells and filtrates of the eight strains, and organic extracts from the two active ones. Extracellular metabolites remained effective after heating at 50-100°C with a decline in activity beyond 100°C, when added with proteinase K and their pH adjusted at 2 and 12. Chitinase and surfactin genes were detected using PCR amplification and sequenced for S. maltophilia CT16 and B. subtilis subsp. inaqosorum CT43, respectively. Five strains have shown chitinase- and proteases-activities. B. subtilis subsp. inaqosorum CT43 and S. maltophilia CT16 were able to produce siderophores and salicylic acid. Hydrogen cyanide production was achieved only with S. maltophilia CT16.