Metabolic analysis of two wheat (Triticum aestivum L.) cultivars in response to Russian wheat aphid (Diuraphis noxia Kurdjumov) infestation
Wheat is one of the most widely consumed cereal grains globally and plays a critical role in food security. As a staple crop in many households, it provides essential nutrients and contributes significantly to daily caloric intake. Although wheat is attacked by multiple pests, the Russian wheat aphid (RWA), Diuraphis noxia, remains one of the most damaging, causing considerable yield losses. While resistance breeding has long been the preferred control strategy, newly emerging RWA biotypes have increasingly overcome previously effective resistance genes. This highlights the need for alternative approaches, with metabolomics emerging as a valuable tool for identifying metabolic biomarkers that can support faster and more effective resistance breeding. This study, therefore, aimed to investigate the effect of the South African Russian wheat aphid biotype 5 (RWASA5) on the metabolic profiles of two wheat cultivars, Tugela and Tugela DN. The cultivars were infested with RWASA5 and harvested at 0, 4, 8, 24, and 48 h post-infestation, followed by untargeted liquid chromatography–mass spectrometry (LC–MS) profiling. A total of 19 metabolites were identified, of which 12 were upregulated and 7 were downregulated. Phenolic compounds were the dominant class, with secoisolariciresinol diglucoside showing a significant increase in Tugela DN following RWASA5 infestation. Flavonoids formed the most abundant phenolic subgroup. Enriched pathways included glycerophospholipid, linolenic acid, and arachidonic acid metabolism. These findings indicate that RWA infestation triggers distinct metabolic shifts in wheat and provide insights into wheat–RWA interactions for crop improvement.