Effectivity of Ammi visnaga (Khella) Methanolic Extract as a Prospective Biocontrol Agent against tomato mosaic virus Infection

Abstract Tomato mosaic virus, formally designated as Tobamovirus tomatotessellati (ToMV) according to Ictv 2025, continues to pose a threat to agriculture due to its rapid spread and resistance to conventional controls. In our study, we evaluated the antiviral efficacy of methanolic Ammi visnaga seed extract (MKSE) as a sustainable biocontrol agent. Using Datura metel as a susceptible host, phytotoxicity assays confirmed that MKSE safe concentrations are 10, 20 and 30 µg/mL (with < 20% phytotoxicity). In phytoantiviral dose–response evaluations using a local lesion assay, MKSE demonstrated a clear and significant dose-dependent effect, with inhibition rates of 66.82% at 10 µg/mL, 78.00% at 20 µg/mL, and 85.64% at 30 µg/mL (p-value < 0.05). Specifically, we investigated the MKSE antiviral mechanisms via post-inoculation treatment that demonstrated an 88.82% suppression of viral replication at 30 µg/mL; simultaneous treatments achieved 85.29% virucidal activity, and pre-inoculation gave 81.76% protection, with all results being statistically significant (p-value < 0.05). Mechanistically, MKSE downregulated PR-2 (β-1,3-glucanase) gene expression by approximately 25-fold, thereby preserving callose deposits at plasmodesmata and indirectly limiting viral movement between host cell. This represents the first-reported antiviral strategy for A. visnaga in plant pathology. This dual action, direct viral inhibition coupled with indirect limitation of viral spread, underscores MKSE’s potential as an eco-friendly alternative to synthetic virucides. Our findings provide the first evidence of A. visnaga ’s efficacy against plant viruses and support its integration into sustainable agricultural practices. Future work will focus on isolating bioactive compounds, field validations, and optimizing nanoformulation delivery strategies.