An alkali-extracted biostimulant prepared from Ascophyllum nodosum alters the susceptibility of Arabidopsis thaliana to the green peach aphid

Extracts from the brown seaweed, Ascophyllum nodosum (ANE), are extensively used as plant biostimulants. Ascophyllum nodosum extracts, as applied to plants, impart resistance/tolerance against various abiotic and biotic stresses due to the presence of multiple biological primers and elicitors. However, little information is available on the effects of ANE on insect pests of crops. Green peach aphid (GPA), Myzus persicae, is an important insect pest and used as an insect model to study insect-plant interactions. In this study, Arabidopsis thaliana was used as a model plant to determine whether application of an ANE conferred any protection from a GPA infestation. Plants treated with ANE had a 13% greater GPA population than the inorganic-treated control. Feeding preference of GPA was not influenced by ANE treatment when the insect was given a choice between the ANE-treated and control plants. Higher plant biomass was observed in ANE treatments with a GPA infestation, as compared to the control. Plants treated with ANE demonstrated better recovery from GPA infestation, as shown by a higher seed yield. Apart from higher GPA numbers, ANE-treated plants exhibited reduced plant tissue damage around the feeding area. Lower expressions of SAG13 and SAG 21 genes indicated that ANE-treated plants delayed their senescence in Arabidopsis. We concluded that treatment of ANE conferred protection from the GPA biotic pressure, while delaying senescence in treated Arabidopsis. Increased GPA numbers, on treated plants could be, in part, associated with delayed senescence of Arabidopsis plants following ANE application.