Silicon dioxide nanoparticles mitigate phytoplasma infection and enhance defense responses in faba bean (Vicia faba L.)

The antiphytoplasmal efficacy of SiO₂NPs was thoroughly evaluated to determine their ability to improve the growth parameters of Vicia faba L. infected with phytoplasma. The highest dose (100 mg/L) achieved the best performance across all measured traits, recording a plant height of 44.8 cm, plant length of 9.48 cm, leaf area of 15.92 cm², leaf count of 23.2 leaves/plant, and fresh weight of 47.44 g. These values were significantly greater than those of the infected plants (28.2 cm, 4.40 cm, 9.32 cm², 15.4 leaves, and 30.96 g, respectively). The 75 mg/L treatment showed similar improvements to the 100 mg/L level in most parameters, while progressively lower doses exhibited reduced, yet still significant, enhancements. Antiphytoplasmal activity enhanced resistance in treated plants. SiO₂NP-treated plants also showed a strong induction of phenolic compounds, reaching 3.9 and 3.6 mg L⁻¹. Analysis of proline content revealed that treatments with 75 and 100 mg L⁻¹ resulted in significant elevations to 76 and 82 mg L⁻¹, compared with the healthy (38.0 mg L⁻¹) and infected (63.0 mg L⁻¹) controls. Moreover, the activity of the defense enzyme (POD) was significantly increased (P ≤ 0.05) to 0.85 and 0.95 at concentrations of 75 and 100 mg L⁻¹, compared with the healthy (0.15) and infected (0.28) controls. (PPO) activity also increased to 0.32 and 0.44 mg L⁻¹, compared with the healthy (0.026 mg L⁻¹) and infected controls (0.080 mg L⁻¹). These findings highlight the promising potential of SiO₂NPs as an effective and biosafe antiphytoplasmal agent.