Stimulating banana tree resistance to banana streak virus (BSV) disease by chitosan nanoparticles

Viral colonization was substantially reduced in banana plants that were foliar sprayed with Citosan NanoParticle, CS-NPs, solution. Banana plants treated with CS-NPs showed different levels of protection against Banana Streak Virus, BSV, compared with the untreated control plants. Banana plants treated with CS-NPs at a rate of 200 mg L −1 , pre-inoculated with BSV, reduced the disease incidence (DI) by 75.00% and disease severity (DS) by 95.3%, compared with untreated plants. Banana plants treated with CS-NPs at a rate of 300 and 400 mg L −1 , pre and post-inoculated with BSV, showed a complete reduction in DI and DS, compared to the control. Surprisingly, the inactivation effects were no longer strong enough to prevent viral accumulation and reproduction after 24h. However, foliar spraying of CS-NPs onto banana leaves significantly reduced BSV replication by activating the plant defense and growth response. The maximum up-regulating expression level of an 18.20-fold change was attained with CS-NPs at a rate of 400 mg L −1 . Simultaneously, the mRNA accumulation of the PR-1 gene in 200- and 300 mg L −1 CS-NPs treated plants was high, with 12.12- and 10.50-relative expression fold increases, respectively, over the untreated control. Plants treated with Cs-NP showed elevated levels of reactive oxygen species (PR1 and PR2), catalase activity, and peroxidase activity. Interestingly, the NPs also markedly raised the phytohormones ABA and SA levels by 160% and 520%, respectively.