Abstract

Background:
Aphids are serious sap-sucking pests that damage okra (Abelmoschus esculentus) and reduce yield through feeding and virus transmission. Conventional insecticides create resistance, environmental pollution, and health hazards. Eco-friendly nanotechnology offers a new direction for insect control using safe, plant-based materials.

Aim:
To evaluate the insecticidal and molecular effects of ZnO nanoparticles derived from Moringa peregrina against Aphis craccivora on okra using ace and COI gene expression analysis.

Methods:
Moringa peregrina seed extract was used to reduce zinc acetate at 70 °C for 2 h under alkaline pH. ZnO nanoparticles were purified and characterized by gravimetric yield (GY), conductometric stability (CS), filtration stability (FS), sedimentation index (SI), and optical density at 600 nm (OD₆₀₀). Aphid-infested okra leaves were treated with three ZnO concentrations (25, 50, 100 µg/mL) and controls. Mortality rates were recorded at 24, 48, and 72 h. Total RNA was isolated from surviving aphids, and cDNA was synthesized. RT-qPCR used ace, COI, and RPS8 and RPL14 primers. The relative expression was calculated by 2^−ΔΔCt.

Results:
Mortality increased significantly with concentration, reaching 85% at 100 µg/mL (p < 0.01). Aphid reproduction decreased by 60% at the same concentration. The methods confirmed ZnO formation at λmax = 370 nm, and the methods showed a mean particle size of 92 nm. RT-qPCR showed the downregulation of ace and COI genes with ΔΔCt values indicating a 4.2- and 3.7-fold reduction, respectively. These molecular reductions were correlated with mortality and decline in reproduction, confirming that nanoparticles induced neural and mitochondrial inhibition.

Conclusion:
Moringa peregrina seed-derived ZnO nanoparticles demonstrated strong aphidicidal action on okra by suppressing both survival and gene expression. These molecular reductions correlated with mortality and decline in reproduction, supporting the hypothesis that nanoparticles induce neural stress and population suppression. Green ZnO nanoparticles are efficient, eco-safe, and suitable for molecular-level pest management.

Key words: Aphis craccivora; Moringa peregrine; Okra; RT-qPCR; ZnO nanoparticles.