Seed priming with beneficial microbes and BABA suppresses beet curly top Iran virus in sugar beet

Sugar beet ( Beta vulgaris L.) is a major industrial crop and an essential global source of sucrose; however, its production is constrained by diseases such as beet curly top disease caused by beet curly top Iran virus (BCTIV; Becurtovirus betae ). This virus induces severe symptoms, including chlorosis, leaf curling, stunted growth, and reduced photosynthetic activity, leading to substantial yield losses, particularly in arid and semi-arid regions. Developing sustainable and effective strategies to manage BCTIV is therefore critically important. In this study, the effects of seed priming with the beneficial microorganisms Bacillus subtilis and Trichoderma zelobreve and the chemical resistance inducer β-aminobutyric acid (BABA), applied individually and in combination, were evaluated for their ability to enhance sugar beet resistance to BCTIV under greenhouse conditions. Two sugar beet genotypes were subjected to different priming treatments, and disease severity, viral accumulation, physiological traits, growth parameters, and defense-related enzyme activities were assessed. All priming treatments significantly reduced disease symptoms and viral DNA accumulation compared with virus-inoculated controls, with the greatest suppression observed in the combined B. subtilis / T. zelobreve /BABA treatment. Plants grown from primed seeds also showed increased chlorophyll content, higher biomass production, improved germination characteristics, and enhanced activities of antioxidant enzymes, including peroxidase, polyphenol oxidase, and catalase. Overall, the results indicate that integrated microbial and chemical seed priming effectively activates plant defense mechanisms. While, supporting growth under viral stress and holding strong potential for application in sustainable sugar beet disease management programs.