Seed bio-/chemo-priming affects the reaction of sugar beet plants to Beet curly top virus-Svr

Beet curly top disease is one of the most important viral diseases that causes economic damage to the yield of beet crops. The present study aimed to evaluate the effect of treating the Paya cultivar of sugar beet with Bacillus subtilis, Trichoderma harzianum, and Beta-aminobutyric acid (BABA), alone and in combination, on the growth and reaction of sugar beet to Beet curly top virus-Svr (BCTV-Svr). Anthocyanin concentration, peroxidase, and polyphenol oxidase enzyme activity were measured by spectrophotometry 14 days post-inoculation (dpi). At thirty dpi, virus accumulation was measured by quantitative polymerase chain reaction (qPCR), and physiological parameters in plants were assessed. The experiments were performed in a factorial, completely randomized design. The first symptoms of BCTV-Svr were observed at nine dpi in the control plants, while the symptoms appeared at 19 dpi in plants treated with B. subtilis, and between 12 and 14 dpi in the other treatments. Plants treated with B. subtilis and BABA showed the lowest and highest severity of the disease, respectively. The results of qPCR were consistent with the symptom severity results, and showed a significant difference in BCTV-Svr accumulation among the treatments. The highest level of anthocyanin concentration was observed in the B. subtilis treatment. On the other hand, polyphenol oxidase and peroxidase activity was increased using viral stress treatments at 14 dpi. The analyses showed that, in general, B. subtilis was more effective in inducing anthocyanin and enzyme activity in healthy and infected plants than the other treatments.