Chitosan–silica nanocomposites induced resistance in faba bean plants against aphids (Acyrthosiphon pisum)

Abstract

Environment-friendly nanostructured materials have been advocated as a promising and green tool for plant disease and insect pest management. It has been shown that chitosan nanoparticles (CNPs) and nanosilica could stimulate plant defenses against biotic stresses. However, to date, it has remained unknown how chitosan–silica nanocomposites mediated the mechanisms underlying the activation of plant resistance against insect herbivores. Herein, the activation effects of chitosan-coated mesoporous silica nanoparticles (CS-MSNs) on faba bean plant resistance against aphids (Acyrthosiphon pisum) were evaluated, as compared to single addition of CNPs and mesoporous silica nanoparticles (MSNs), respectively. Our results showed that foliar spray of 100 mg L⁻¹ CS-MSNs reduced aphid reproduction in terms of nymph aphid population more effectively than equivalent application doses of CNPs, MSNs, and the acetamiprid pesticide. CS-MSNs decreased reproduction by 55.1% after 7 days post aphid infestation as compared to the control. Furthermore, CS-MSN application significantly reduced leaf oxidative stress in response to aphid attacks by increasing the activities of antioxidant enzymes (SOD, POD, CAT). The activation mechanism of CS-MSN-induced plant insect resistance was dependent on activating endogenous signals (Ca²⁺ influx and phytohormone accumulation) and enhancing defense metabolite (e.g., coumarin, quercetin) production. Altogether, CS-MSNs could act as an alternative control tool to simultaneously induce host plant resistance against herbivores and reduce the use of pesticides in agroecosystems.