Effects of light-emitting diode treatments on Brevicoryne brassicae performance mediated by secondary metabolites in Brussels sprouts

Although short-wavelength light and especially UV radiation can induce resistance in plants against herbivorous insects, the optimal wavelengths, light intensities (photon flux rates), and illumination schedules for inducing resistance have not been previously determined. Light-emitting diode (LED) illumination enables researchers to subject insects and plants to narrow-banded light treatments. In this study, we assessed how the metabolite-based defense response in Brussels sprout plants (Brassica oleracea var. gemmifera) against the cabbage aphid, Brevicoryne brassicae (Hemiptera: Aphididae), was affected by the following LED-generated wavelengths of light: 300 nm (UV-B), 365 nm (UV-A), 470 nm (blue light), and 660 nm (red light). Ambient greenhouse light supplemented with light from sodium vapor lamps served as the control treatment. The results showed a significant reduction in B. brassicae performance in the UV-A treatment compared to the blue light treatment; the reduction in the UV-A treatment was accompanied by a significant increase in glucosinolate concentrations. The UV-B treatment induced significant changes in plant flavonoid concentrations but did not affect B. brassicae performance.