Biocontrol and Plant Growth-Promoting Bacteria from Healthy Oases as a Sustainable Strategy Against Bayoud Disease in Date Palm

Bayoud disease, caused by Fusarium oxysporum f. sp. albedinis (FOA), poses a severe threat to date palm (Phoenix dactylifera L.) cultivation in North Africa. Biological control using antagonistic microorganisms represents a promising sustainable strategy to protect date palms. In this study, healthy oases (Tolga and Foughala) in the Biskra region of Algeria were explored for potential biocontrol agents. A total of 115 bacterial isolates were obtained from rhizosphere soils and roots of healthy date palms, among which six strains exhibited strong antifungal activity against FOA in dual culture assays. Molecular identification revealed that GF17, TF6, and GR2 belonged to Bacillus spp., while TT11, GT15, and TF13 were assigned to Actinobacteria (Gordonia terrae, Streptomyces sp., and Microbacterium sp., respectively). Antagonistic activity varied depending on culture media, indicating media-driven differences in metabolite production. Volatile organic compounds showed no significant inhibition of FOA. In vivo assays on germinated seeds demonstrated notable protection by strains GT15, TT11 and GR2. Additionally, these isolates tolerated various abiotic stresses and displayed multiple plant growth promoting (PGP) traits, including extracellular enzyme production. Under hydroponic conditions, treated seedlings exhibited improved root architecture, enhanced fresh biomass, and increased chlorophyll content. These findings highlight the potential of selected PGPR strains as effective biocontrol agents for managing Bayoud disease and promoting date palm growth in affected regions.