Role of exogenous elicitors in canola plant defense against cabbage aphid by regulating physiological balance and secondary metabolite biosynthesis

Induced resistance in plants can be manipulated by the application of elicitors. In this research, the effects of salicylic acid (SA), chitosan, γ-aminobutyric acid (GABA), Serenad Aso ( Bacillus subtilis QST713), and integrated application of these elicitors were studied on the induced resistance of canola to the cabbage aphid, Brevicoryne brassic ae L. (Hem: Aphididae). In the field experiments (during 2019 and 2020), the number of B. brassicae attracted to canola plants treated with different inducers was significantly lower compared to control plants. The lowest population density of this aphid was observed under treatments of SA + GABA and SA + chitosan. Moreover, the positive effect of the integrated application of SA and chitosan/GABA on canola growth parameters was significantly obvious in our study. The highest amounts of glucosinolates and total phenol were recorded in SA + GABA treatment. The contents of energy resources (sugar, lipid, and glycogen) of B. brassicae were lowest when fed on plants treated with SA integrated with GABA /chitosan. Furthermore, the activity of catalase, esterase, peroxidase, and glutathione S- transferase enzymes was the lowest on SA + GABA and SA + chitosan treatments. We concluded that these elicitors cause resistance induction of canola plants to the cabbage aphid. These findings especially suggested that SA integrated with GABA /chitosan on canola plants act successfully for reducing the B. brassicae population and can be considered in integrated management programs of this aphid.