Green Synthesized Silver Nanoparticles Mitigate Biotic Stress Induced by <i>Meloidogyne incognita</i> in <i>Trachyspermum ammi</i> (L.) by Improving Growth, Biochemical, and Antioxidant Enzyme Activities

Abstract

<i>Meloidogyne incognita</i> is an important plant-parasitic nematode that causes significant crop losses all over the world. The primary control strategy for this pathogen is still based on nematicides, which are hazardous to human health and the environment. Considering these problems, this study aimed to determine the efficacy of different concentrations (25, 50, and 100 ppm) of silver nanoparticles against <i>M. incognita</i> on <i>Trachyspermum ammi</i>. Silver nanoparticles synthesized from <i>Senna siamea</i> were thoroughly characterized using various physicochemical techniques, viz., UV-visible spectrophotometer, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy-dispersive X-ray analyzer (EDX). Results revealed that plants treated with 50 ppm silver nanoparticles one week before <i>M. incognita</i> inoculation (T₂) exhibited maximum and significant (<i>p</i> ≤ 0.05) increases in plant growth, biochemical characteristics, and activities of defense enzymes such as peroxidase, catalase, superoxide dismutase, and ascorbate peroxidase over the inoculated control (IC) plants. Furthermore, the maximum reduction in the number of galls, egg masses, and root-knot indices was recorded in plants treated with 100 ppm silver nanoparticles (T₃) followed by plants treated with 50 ppm silver nanoparticles before nematode inoculation (T₂), over inoculated plants (IC). Anatomical studies showed accumulation of lignin in the transverse section (TS) of roots treated with 50 ppm silver nanoparticles. As a result, the present finding strongly suggests that silver nanoparticles synthesized from <i>S. siamea</i> had nematicidal activity, and it could be an efficient, safe, cost-effective, and affordable alternative to chemical nematicide.