Efficacy of Certain Monoterpenes as Antifungal Agents and Abiotic Elicitors Against Chocolate Spot Disease of Faba Beans Caused by Botrytis fabae

Chocolate spot, caused by the ascomycete fungus Botrytis fabae, is a devastating foliar disease and a major constraint on the quality and yield of faba beans (Vicia faba). Monoterpenes, such as carvone, cineole, and linalool, are often considered natural-identical alternatives to synthetic chemicals. Therefore, this study was carried out to assess the antifungal activity of some eco-friendly control agents (carvone, cineole, and linalool) against B. fabae, the causative agent of chocolate spot disease in faba beans, through growth inhibition assays in vitro. Furthermore, the efficacy of the tested monoterpenes for reducing the severity of chocolate spot disease in faba beans was evaluated under field conditions. Moreover, these eco-friendly control agents activate plant defense enzymes (phenylalanine ammonia-lyase, polyphenol oxidase, and peroxidase) as a self-defense mechanism against pathogen attacks of faba bean plants were investigated. Moreover, the impact of the tested monoterpenes on growth and yield characters of faba bean was evaluated. The results indicated a significant decrease in B. fabae growth following a treatment with the tested compounds compared to untreated controls. In field trials, treated faba bean plants exhibited a notable reduction in disease severity. Additionally, the application of monoterpenes enhanced the activity of defense enzymes (phenylalanine ammonia-lyase, polyphenol oxidase, and peroxidase), which are integral to plant defense mechanisms. Treatments also resulted in significant improvement growth and yield characters of faba bean. These findings suggest that the tested monoterpenes could serve as a control strategy for managing B. fabae, offering an environmentally sustainable alternative to conventional fungicides.