When Metabolomics Meets Quantitative Genetics: An Integrative Strategy to Elucidate Plant Resistance Mechanisms

Gene pyramiding in crop varieties offers a promising strategy to achieve sustainable production and reduce reliance on pesticides. However, stacking resistance genes without understanding their biological functions may result in transient protection. Although numerous studies have mapped loci associated with resistance to biotic stresses, the underlying molecular mechanisms remain poorly characterised. Resistance genes are often involved in pest/pathogen recognition, whereas quantitative trait loci (QTLs) may act in other steps of plant immunity such as signalling and defence pathways. In parallel, specialised metabolites have attracted growing attention as key defence components, acting as antimicrobial or repellent agents. While both fields encounter challenges to precisely decipher plant defence mechanisms, making use of metabolomics on segregating populations could bypass some of these limitations. In this review, we introduce an approach based on the identification of metabolic QTLs within populations where resistance QTLs segregate, enabling the detection of genomic co-localisations between both types of QTLs. This integrative framework can reveal specific metabolic signatures associated with resistance, thus refining hypotheses on the mode of action of resistance QTLs. Ultimately, elucidating the genetic architecture of specialised metabolism in relation to quantitative resistance will inform on more effective combinations of defence mechanisms for breeding resistant varieties.