Synergy of La and low-dose LG2 for alleviating aphid stress in sorghum: A novel strategy for reduced chemical input

To devise an efficient and low-toxicity strategy for aphid control, this study assessed the impacts of five spray treatments on sorghum exposed to 48-hour aphid stress. The treatments included lanthanum (La) alone, dimethoate (LG1) alone, La+LG2, La+LG3, and La+LG4. Among them, the La+LG2 treatment exhibited the most superior performance. La+LG2 significantly enhanced plant growth, as evidenced by increases in plant height, fresh weight, and dry weight. It also reduced cell membrane damage, as indicated by lower malondialdehyde (MDA) levels and relative electrical conductivity. In terms of photosynthesis, La+LG2 elevated the P-phase fluorescence intensity of the OJIP curve, improved the maximum quantum yield of photosystem II (Fv/Fm), optimized the energy distribution within photosystem II (increasing electron transport flux per reaction center, ETO/RC, and trapped energy flux per reaction center, TRO/RC, while decreasing absorbed energy flux per reaction center, ABS/RC, and dissipated energy flux per reaction center, DIO/RC), and promoted pigment synthesis. Additionally, La+LG2 alleviated oxidative damage by activating enzymatic antioxidants, including superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and glutathione peroxidase (GSH-PX). It also optimized the ascorbic acid-glutathione (ASA-GSH) cycle to scavenge reactive oxygen species (ROS) and maintain redox homeostasis. Meanwhile, at the molecular level, La+LG2 constructed a dual-regulatory network to enhance photosynthetic efficiency and maintain the homeostasis of reactive oxygen species (ROS). This was accomplished via the synergistic activation of photosynthesis-related genes and the differential regulation of respiratory burst oxidase homolog (Rboh) family genes. Overall, La+LG2 achieved an efficacy comparable to that of high-dose LG1 but with reduced chemical input. This reveals a multi-targeted stress regulation mechanism and provides theoretical support for the synergistic pest control strategy combining rare earth elements and low-toxicity agents, as well as for agricultural efforts to reduce pesticide use. • Evaluated sorghum’s response to La, LG1, La+LG2/3/4 under aphid stress. La+LG2 showed the best mitigation effect. • La+LG2 boosted sorghum growth (height, fresh/dry weight) and reduced membrane damage (lower MDA, relative conductivity). • La+LG2 improved sorghum photosynthesis (OJIP P-phase, Fv/Fm, optimized PSII energy distribution, pigment synthesis). • La+LG2 activated enzymatic antioxidants (SOD, POD etc.) and ASA-GSH cycle to scavenge ROS. • La+LG2, through the synergistic activation of genes related to photosynthesis and the differential regulation of respiratory burst oxidase homolog (Rboh) genes, constructs a dual-regulatory network aimed at enhancing photosynthetic efficiency and maintaining the homeostasis of reactive oxygen species (ROS). • La+LG2 matched high-dose LG1’s efficacy with less chemicals, supporting agricultural “green pesticide reduction”.