Sustainable approaches to manage fusarium root rot in faba bean.

Faba bean (Vicia faba L.) is a major legume crop with high nutritional and commercial value, but its output is severely limited by vascular wilt and root rot caused by Fusarium oxysporum. Biological control and other environmentally benign solutions provide long-term alternatives to toxic fungicides. Under controlled conditions, the cyanobacterium Trichormus variabilis and the endophytic bacterium Priestia endophytica were tested for their biocontrol potential against Fusarium oxysporum. Plant defense responses were evaluated using total phenols, proline, and peroxidase activity. Infection with Fusarium oxysporum significantly raised stress indicators, such as phenols (71.97 mg g⁻¹), proline (5.54 mg g⁻¹), and peroxidase (6.35 U g⁻¹). Single treatments of either bioagent reduced stress, decreased phenolic buildup, and restored enzymatic equilibrium. The combination treatment offered the strongest protection, decreasing stress indicators to 58.9 mg/g phenols, 3.42 mg/g proline, and 4.54 U/g peroxidase. Bioagents increased soil microbial activity, including dehydrogenase (4.69 mg TPF g⁻¹ soil in Trichormus variabilis vs. 2.5 in Fusarium oxysporum), chitinase (4.07 U mL⁻¹ in the combined treatment vs. 1.40 in control), and protease (4.50 U g⁻¹ soil in the combined treatment vs. 1.70 in control). The enzymatic stimulation increased plant health and resistance. Trichormus variabilis and Priestia endophytica had a synergistic impact against Fusarium oxysporum, making combination application the most promising technique for long-term management of faba bean root rot.