Antifungal Activity of Garlic (Allium sativum L.) Essential Oil and Hydrosol Against Zymoseptoria tritici, the Causal Agent of Septoria Tritici Blotch in Bread Wheat

Septoria tritici blotch (STB), caused by Zymoseptoria tritici , is one of the most damaging foliar diseases of bread wheat ( Triticum aestivum L.), leading to severe yield losses and increasing reliance on synthetic fungicides. The emergence of fungicide-resistant populations and growing environmental concerns highlight the need for sustainable alternative control strategies. In this study, the antifungal activity of essential oil (EO) and hydrosol obtained from a local Algerian red garlic ( Allium sativum L.) variety was evaluated in vitro against Z. tritici. Garlic extracts were characterized through morphological, physicochemical, and chemical analyses, with EO volatile composition determined by GC–MS. Twenty-one compounds accounting for 99.97% of the total EO composition were identified, dominated by organosulfur compounds, particularly diallyl trisulfide (36.99%) and diallyl disulfide (35.78%). Antifungal assays revealed a strong dose-dependent inhibition of mycelial growth. Garlic EO completely inhibited fungal growth at 0.30 µL mL⁻¹, although a reduction in efficacy over time suggested limited stability. Notably, garlic hydrosol achieved complete and stable inhibition at 150 µL mL⁻¹, despite its lower sulfur content, representing a novel and underexplored approach for STB control. These findings demonstrate the potential of garlic-derived EO and hydrosol as eco-friendly antifungal agents and support their possible integration into sustainable disease management strategies for wheat, contributing to the reduction of chemical fungicide inputs.