افزایش اثربخشی کنترل زیستی Bacillus subtilis در برابر ویروس پیچیدگی برگ زرد گوجه فرنگی از طریق درونپوشانی با کیتوزان

In plant protection, the use of chitosan has effectively solved the main limitations of bacteria encapsulation technology, including survival, long-term performance and degradability. However, more precision is needed to improve the encapsulation of probiotic bacteria for use in integrated pest and plant disease management programs. The efficacy of using chitosan for the encapsulation of biocontrol bacteria requires further study. Here, Bacillus subtilis strain PVRC02 was encapsulated using chitosan with ultra-low (ULMWC, 20 kDa), low (LMWC, 50 kDa), medium (MMWC, 150 kDa) or high (HMWC, more than 300 kDa) molecular weight. Treatments were applied via foliar spray before the TYLCV inoculation by viruliferous white flies. Then, we measured disease incidence, plant growth parameters, virus quantity, resistance-related gene expression, and defense enzyme activity to evaluate its antiviral activity against the viral infection in tomato plants. The results showed that B. subtilis strain PVRC02 micro-capsulated with MMWC chitosan induced excellent resistance against TYLCV. Moreover, an improvement in plant growth and biomass yield parameters was observed. MMWC lowered the infection rate (48.27%). The Growth parameters including, fresh weight (54.3%), plant height (44.3%) and leaf area index (47.5%) were significantly improved in tomato following MMWC treatment. Results showed a significant reduction of TYLCV accumulation in PVRC02 strain micro-capsulated with MMWC-treated plants that were successively infected with TYLCV, compared to control treatment (only TYLCV-infected plants). PVRC02 strain micro-capsulated with MMWC-treated upregulated expression of pathogenesis-related ICS1, ERF-A2, PR1 and PR2 genes, and boosted activities of enzymes related to defense responses (phenylalanine ammonia lyase, peroxidase, and superoxidase) in tomato leaves. This study showed that the use of medium molecular weight chitosan for encapsulating B. subtilis strain PVRC02 improved the defense responses of tomato plants against TYLCV better than chitosan with lower and higher molecular weights.