Genotype-dependent responses to foliar-applied insoluble phosphorus in wheat are associated with leaf-surface metabolite profiles

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Phosphorus (P) deficiency constrains plant development, highlighting the need to identify traits associated with improved P acquisition under nutrient-limited conditions. Here, we examined genotype-dependent responses of wheat introgression lines (ILs), derived from wild emmer ('Zavitan') × durum wheat ('Svevo'), to foliar application of P-rich dust under low-P conditions. Across three experiments, IL105 and its wild parent 'Zavitan' showed consistent increases in biomass following dust application, whereas IL104 showed little or no positive response. In Exp. 2, dust application also increased shoot P accumulation (P offtake) in IL105, whereas IL104 showed no corresponding increase. Leaf-surface metabolite profiling under contrasting P supply revealed a broader increase in the abundance of organic acids, sugars, and amino acids on IL105 leaves under P deficiency, whereas these treatment-associated shifts were weaker or absent in IL104. Structural differences between the contrasting lines were more limited, and the epidermal traits measured here did not fully correspond with the contrasting responses to dust application. Comparative analysis of introgressed regions indicated that IL105 carries extensive wild-emmer-derived genomic segments containing genes annotated for metabolite production, transport, and P-related processes, representing candidate regions for future functional validation rather than evidence of a defined mechanism. Collectively, these results show that wheat responses to foliar insoluble P vary among genotypes and are more consistently associated with leaf-surface metabolite profiles than with the epidermal traits measured in this study.