Microbial bio-inducers and seaweed extract enhance tomato immunity and physiological responses against Fusarium oxysporum

Fusarium oxysporum significantly reduces tomato crop yields. While chemical fungicides can suppress the pathogen, they often harm the environment and lead to increased fungal resistance. Biocontrol, using antagonistic bacteria, offers an eco-friendly alternative by enhancing plant resistance and suppressing Fusarium through competition and antimicrobial activity. This study evaluated the effectiveness of plant growth-promoting rhizobacteria (PGPR) and Ascophyllum nodosum (Alga Mix®) in boosting tomato plant immunity. Twenty bacterial isolates were collected from the tomato rhizosphere in Eltal Elkbeer, Ismailia, Egypt, and assessed for their ability to produce hydrocyanic acid production (HCN), siderophores, and Indole-3-acetic acid (IAA). Two isolates exhibited the highest activity and antifungal properties against F. oxysporum. Molecular identification confirmed them as Bacillus subtilis and Achromobacter insuavis. Under greenhouse conditions, infected tomato plants treated with these agents showed reduced disease severity and improved physiological parameters. Alga Mix® was particularly effective, enhancing chlorophyll content, carotenoids, and phenolic compounds. Treatments also boosted enzymatic defenses and mitigated oxidative stress. These findings support the potential of PGPR and Alga Mix® as sustainable strategies for managing Fusarium wilt in tomatoes.