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

Highlights

• •Camel urine priming enhances barley resistance against Fusarium graminearum
• •Mitigates Fusarium-induced oxidative stress, preventing significant growth reduction under infection.
• •Boosts antioxidant defenses
• •Enhances secondary metabolism,especially in later infection stages.
• •Sustains antifungal enzyme activity.

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.

Introduction

Fusarium graminearum is a devastating fungal pathogen affecting cereals, including barley, wheat, and maize. It is notorious for causing Fusarium head blight and crown rot, which leads to significant economic losses and grain quality reduction due to mycotoxin contamination. There is a growing need for new natural and effective ways to control Fusarium graminearum, which arises from the limitations and challenges associated with conventional methods. These include chemical fungicide resistance, environmental concerns, and consumer demand for sustainable agricultural practices.

Seed priming is a promising technique for managing plant diseases. By pre-treating seeds with bioactive substances, priming enhances seedling vigor, improves plant defenses, and reduces disease severity. Priming can improve germination uniformity and speed, leading to healthier and more robust seedlings that are better equipped to resist pathogens. Also, priming activates plant defense pathways against pathogen attack, enhancing the plant’s ability to combat infections (Deshmukh et al., 2020; Zulfiqar, 2021; Riseh et al., 2022). Besides, treating seeds with antifungal agents or biocontrol organisms (priming agents) can directly inhibit the growth of pathogens on the seed surface or in the rhizosphere (Miljaković et al., 2024). Enhanced root development from priming improves plant nutrition, reducing stress that could otherwise make plants more susceptible to diseases (Lee and Kasote, 2024). Priming can ensure sustainable disease control by reducing the need for repeated chemical fungicide applications. Especially with biological or natural elicitor-based priming, this approach minimizes environmental impact. Also, priming is a cost-effective control way as it requires smaller quantities of treatment agents compared to field sprays (Sen and Das, 2024). One of the biggest challenges in priming is choosing the priming agent that does not adversely affect seed viability or germination, thus exploring new, cheap-effective priming agents considers plant disease control.

Camel urine sample

It has been traditionally used in certain cultures for its medicinal properties, including antimicrobial activity. Scientific studies have started to confirm some of these claims, showing that camel urine shows inhibitory effects against various bacterial, fungal, and viral pathogens. This antimicrobial potential is attributed to its unique composition, including bioactive compounds such as enzymes, minerals, and metabolites with bactericidal or fungicidal properties (Gole, 2020; Iglesias Pastrana et al., 2022; Amina et al., 2024a, 2024b). Several studies have demonstrated the antifungal potential of camel urine against a variety of fungal pathogens, including Aspergillus niger, Fusarium oxysporum, Rhizoctonia solani, Sclerotinia sclerotiorum, and Candida albicans. Camel urine exhibits antifungal activity through multiple mechanisms. One primary action is its high content of bioactive compounds, including urea, phenols, and various minerals, which create an inhospitable environment for fungal growth (Bakhsh et al., 2023). Urea, in particular, has a protein-denaturing effect that can disrupt fungal cell wall integrity (Dars et al., 2019). Phenolic compounds contribute to oxidative stress in fungal cells, damaging cellular components such as membranes, proteins, and DNA.

Moreover, camel urine’s alkaline pH and high osmolarity can impair fungal metabolism and spore germination (Atasoy et al., 2024). Some studies also suggest that camel urine may interfere with fungal enzymatic systems and inhibit the production of mycotoxins, thereby reducing pathogenicity (Iglesias Pastrana et al., 2022; Amina et al., 2024a, 2024b). The antimicrobial activity of camel urine makes it a potential agent for plant disease control. This study explores the impact of camel urine priming on barley seedling growth, disease resistance, and metabolic responses, particularly to Fusarium graminearum infection. By comparing camel urine-primed seeds with hydro-primed and untreated controls, we assess its effects on growth, biomass, and disease reduction. Biochemical changes, such as antioxidant enzyme activity and secondary metabolites, alongside antifungal enzyme activities like β-glucanase and chitinase are examined. This research highlights the potential of camel urine priming as a natural solution for enhancing plant health and combating fungal pathogens, offering a sustainable approach to crop protection.

Chemicals and reagents

All chemicals and reagents used in this study were of analytical grade and purchased from reputable suppliers. The phosphate buffers (pH 6.5 and 7.8), disodium ethylenediaminetetraacetate (EDTA), sodium chloride (NaCl), methanol, trichloroacetic acid (TCA), thiobarbituric acid (TBA), pyrogallol, catechol, hydrogen peroxide (H₂O₂), and potassium phosphate buffer were purchased from Merck (Germany). Nitro blue tetrazolium (NBT), L-methionine, and riboflavin used in the superoxide dismutase (SOD)

Effect of camel urine priming on barely seedlings growth and disease reduction

Fusarium infection significantly reduced barley growth (supplementary data Fig. S2), causing a decrease of approximately 44.57 %. In the camel urine-primed group, Fusarium infection resulted in a non-significant reduction in growth, with the infected camel urine-primed group showing 9.38 % lower growth compared to the healthy camel urine-primed group. However, the infected camel urine-primed group showed no reduction in growth compared to the control and showed 2.28 % more growth than the

Discussion

Fusarium graminearum is a pathogenic fungus responsible for crown rot in various cereal crops, especially wheat and barley. This disease poses significant challenges to agricultural productivity by attacking the crown and basal stem tissues of plants. The present study showed the significant negative effect of Fusarium graminearum on barely growth, causing seedling wilting and dryness. The infection leads to necrosis of the crown and root tissues, compromising the plant’s structural integrity

Conclusion

This study demonstrates the significant adverse effects of Fusarium graminearum infection on barley growth, including reduced fresh and dry weight, moisture loss, and elevated oxidative stress markers such as H₂O₂ and MDA. Camel urine priming (7 %) proved effective in mitigating these impacts by enhancing the plant’s antioxidant defenses, preserving growth under infection, and reducing disease severity by 84.53 %. This was achieved through the activation of antioxidant enzymes (SOD, POX, PPO).

Ethical approval

This research article does not contain any studies with human participants or animals performed.

Summary

“This study explores the potential of camel urine as a natural priming agent to enhance barley’s defense mechanisms against Fusarium graminearum, a major fungal pathogen responsible for Fusarium head blight. The findings reveal that camel urine treatment activates a range of physiological and biochemical defense responses in barley, including the upregulation of antioxidant enzymes and pathogenesis-related proteins. These responses collectively strengthen the plant’s resistance to fungal infection, suggesting that camel urine could serve as a sustainable and cost-effective strategy for improving crop protection in environmentally friendly agricultural practices.”