Camel urine-priming induced defense mechanisms in barley against Fusarium graminearum

Abstract

Fusarium graminearum poses a major threat to barley production worldwide. While seed priming is a promising strategy to enhance plant defense, the use of unconventional priming agents remains underexplored. This study investigates the protective effects of pre-infection camel urine seed priming on barley seedlings challenged with Fusarium graminearum, focusing on growth, disease resistance, oxidative stress, and defense-related responses. Barley grains were primed with camel urine and grown in both Fusarium-infested and uninfested soils. Fusarium infection initially triggered a sharp increase in oxidative stress markers reflecting an early oxidative burst commonly associated with defense signaling. However, in hydro-primed seedlings, this response persisted, leading to sustained oxidative damage and growth suppression. In contrast, camel urine priming modulated the oxidative burst effectively, initially permitting H₂O₂ accumulation for defense activation, followed by a rapid decline, resulting in an 84.53 % reduction in disease severity and maintenance of seedling growth under infection. This was accompanied by enhanced antioxidant defenses, as indicated by significantly increased activities of antioxidant enzymes, and a 145 % increase in total antioxidant capacity compared to control. Camel urine priming also showed a reduction in shikimic acid levels under infection, suggesting increased metabolic flux toward the phenylpropanoid pathway. Thus, phenylalanine ammonia-lyase activity, phenolic compounds, and flavonoids were significantly elevated. Antifungal enzymes, β-glucanase and chitinase, also remained high in camel urine-primed seedlings, in contrast to their sharp decline in hydro-primed controls. These findings highlight camel urine priming as a promising, sustainable approach for managing Fusarium in barley.