Phenolic acids and grain protein content in wheat landraces and cultivars under zero nitrogen supply

Phenolic acids are the primary phenolic compounds in wheat with significant health-promoting benefits. Understanding the influence of nitrogen (N) supply on phenolic acid content in wheat genetic resources is crucial to ensure high grain quality under sustainable agricultural systems. In this study, 29 durum and bread wheat landraces and cultivars were grown under two different N levels (0 and 80 kg N ha 1 ) over two years. Phenolic acid accumulation and grain protein content (GPC) were evaluated in relation to yield components. Results showed a strong N level × year interaction for both grain yield and quality traits. A significant increase in GPC was observed at higher N supply both in durum and bread wheat across the two years. At N0, compensatory effects were detected for grain yield per spike and thousand-kernel weight. The six major phenolic acids, typically identified in wheat, were quantified. Among these, ferulic acid was the most abundant, showing a slight increase under N0. Correlation analyses showed negative relationships of phenolic acids and GPC with yield components, suggesting a trade-off between primary growth and secondary metabolite production. By applying ferulic acid and grain protein deviation indices, we identified durum and common wheat genotypes, especially landraces and old cultivars, retaining high phenolic acids and GPC under N0 conditions. Overall, these results suggest that wheat landraces and old cultivars could be a valuable choice for cultivation in low-N input, in view of more sustainable agricultural systems, especially in marginal areas.