Plant growth promoting and inducible antifungal activities of irrigation well water-bacteria

Different bacterial groups in irrigation well water are strongly implicated in soil health and plant development. Herein, 48 bacterial strains were isolated from agricultural well water in northern Algeria. Among them, four strains were selected based on their antifungal potential and their ability to express Plant Growth Promoting traits such as Indole Acetic Acid (IAA), hydrolytic enzymes, siderophores etc. The isolates were identified as Pseudomonas sp. (B, D and N strains) and Serratia sp. (C strain) by 16S rRNA gene sequencing. Mycelial growth inhibition against Botrytis cinerea and Aspergillus niger ranged from 60 to 90% for the four strains. Moreover, volatiles compounds emission by the isolates resulted in Plant Growth Inhibition values ranging from 13 to 50%, specifically against B. cinerea. Impressively, the strains' antifungal activity showed high inducibility as it was obtained only by the filtered supernatants from bacterial cultures previously in contact with the fungus. Finally, a greenhouse assay, carried out to determine the strains' efficacy in promoting plant growth and protecting seedlings under Pythium aphanidermatum-infected soil, revealed that the strain N markedly enhanced pea germination (+250%) and fresh weight (+43%) and tomato fresh weigh (+10%). The results constitute an attempt for better use of the bacterial functional diversity from irrigation wells in sustainable agriculture.