Methyl jasmonate modulates non-enzymatic antioxidant defenses in sugarcane under Diatraea saccharalis (Fabricius, 1794) infestation

Sugarcane is exposed to several biotic stresses that limit productivity, with herbivory by the sugarcane borer Diatraea saccharalis (Fabricius, 1794) (Lepidoptera: Crambidae) being one of the most damaging. Larvae bore into stalks, disrupt sap flow, facilitate fungal and bacterial infections, and ultimately reduce plant performance and juice technological quality, while triggering an oxidative burst. In this context, defense priming offers a sustainable, cost-effective complement-and in some scenarios, an alternative-to insecticide-based control, by enhancing plant readiness rather than suppressing pests directly. The exogenous application of methyl jasmonate (MeJA) has emerged as a promising strategy to induce plants' natural defenses by activating mechanisms similar to those triggered by pest attack. This study aimed to evaluate how exogenous MeJA modulates non-enzymatic antioxidant defenses in sugarcane under herbivory by D. saccharalis and under non-stress conditions. The experiment followed a randomized block design in a 2 × 4 factorial scheme with five replicates. The main factor was stress condition (with or without borer infestation), and the second factor was MeJA concentration (0, 0.25, 0.5, and 1 mmol L⁻¹), applied seven days before infestation. Leaf samples were collected to assess lipid peroxidation [malondialdehyde (MDA)], non-enzymatic antioxidants (total phenolics, carotenoids, ascorbate and glutathione), total chlorophyll and anthocyanin index. Exogenous MeJA activated antioxidant defense pathways in both stressed and non-stressed plants in a dose- and context-dependent manner. Under borer infestation, the highest MeJA concentration (1 mmol L⁻¹) enhanced defense responses, increasing phenolic compounds and carotenoids while significantly reducing MDA levels. In non-stressed plants, the lowest MeJA dose (0.25 mmol L⁻¹) was more effective, lowering MDA and promoting the accumulation of phenolics, glutathione and anthocyanins. These results close an important gap on MeJA-sugarcane-borer interactions and suggest that different MeJA dose ranges could be strategically explored as complementary tools in integrated borer management, a hypothesis that now deserves validation under field conditions.