Chitosan‐Based Ribavirin and Acyclovir Nanoformulations Suppress Bean Yellow Mosaic Virus and Modulate PR5 and PR3 Expression in Faba Bean

ABSTRACT

Bean yellow mosaic virus (BYMV) is a major constraint to faba bean ( Vicia faba L.) production, causing severe symptoms and substantial yield losses. This study evaluated the antiviral potential of ribavirin‐loaded chitosan nanoparticles (RIB‐CSNPs) and acyclovir‐loaded chitosan nanoparticles (ACV‐CSNPs) for BYMV management, together with their effects on disease development, physiological performance, biochemical responses and defence‐related transcript accumulation. Chitosan nanoparticles were synthesised by ionic gelation using sodium tripolyphosphate (TPP) and applied at concentrations of 100–400 μg mL ⁻¹ , either 24 h before or 24 h after BYMV inoculation. The experiments were conducted in two independent trials ( n  = 6). Direct virus detection was supported by RT‐PCR and treatment‐wise DAS‐ELISA, which showed lower BYMV absorbance values in nanoparticle‐treated plants than in the infected control, with the greatest reduction under RIB‐CSNP treatments, particularly at 300 and 400 μg mL ⁻¹ . Among the tested treatments, RIB‐CSNPs exhibited the highest antiviral activity, achieving up to 85% inhibition with the lowest disease severity. RIB‐CSNP treatment also significantly improved chlorophyll content, total phenolics, proline accumulation and antioxidant enzyme activities, including peroxidase (POD) and catalase (CAT). In addition, growth and yield‐related traits, including leaf area, number of pods per plant and number of seeds per plant, were markedly enhanced, particularly at 300 and 400 μg mL ⁻¹ . In contrast, ACV‐CSNPs showed lower antiviral efficacy than RIB‐CSNPs, although they still improved plant performance and were associated with differential defence‐related transcript responses. Relative expression analysis indicated marked induction of PR5 (thaumatin‐like protein), especially under post‐inoculation treatment with RIB‐CSNPs, whereas PR3 (chitinase) showed a more selective response and was more responsive to ACV‐CSNPs at intermediate concentrations. Overall, chitosan‐based antiviral nanoformulations, particularly RIB‐CSNPs, show promise as a strategy for reducing BYMV‐associated damage and improving the performance of faba bean plants.