A double-edged sword: Biofortifying fruit crops with Selenium nanoparticles

Selenium (Se) is an essential trace element for humans, impacting multiple key physiological processes in fruit crops, including secondary metabolism and ripening. Among different methods applied, literature provides evidence of the effectiveness and safety of applying selenium nanoparticles (SeNPs) as a tool for plant biofortification. SeNPs are typically biologically or chemically produced 2-282 nm particles of elemental Se (Se0) coated with an organic membrane, with unique physicochemical properties, often allowing them to be less toxic and more bioavailable compared to mineral Se. The biofortification of fruit crops with SeNPs has not been extensively reviewed. The aim of this work is to identify specific and common trends in the effects of SeNPs application across different fruit crops. SeNPs applied at concentrations of up to 50 mg L-1 in irrigation or up to 100 mg L􀀀 1 as foliar spraying showed, in general, positive effects on growth, yield, nutraceutical value, biochemical composition, antioxidative state, improved responses to abiotic stresses in tomato, cucumber, strawberry, physalis, persimmon, orange, lime, grape, pomegranate, apple, mango, date, and pepper. In the latest, SeNPs increased the yield up to 53%, and phenols up to 75%. SeNPs enhanced drought, heat, and salinity resistance, activated defense-related mechanisms by upregulating lipoxygenase (LOX), phenylalanine lyase (PAL), β 1,3-glucanase (GLU), superoxide dismutase (SOD), and reduced Reactive Oxygen Species (ROS). In addition to that, postharvest spraying, submerging, or coating fruit in up to 150 mg L- 1 SeNPs resulted in inhibition of bacterial, and fungal pathogens, including Alternaria spp., Botrytis spp., Fusarium spp., and nematodes Meloidogyne spp