Root-driven SOC accrual and stabilization in new perennial wheat genotypes: The importance of architectural and morphological root traits

Perennial grains are increasingly proposed as climate-smart options to enhance soil organic carbon (SOC) while maintaining agronomic production, yet frameworks linking genotype-specific root traits to SOC persistence remain limited. Here, a trait-based approach was applied to quantify how architectural, morphological, and chemical root traits shape SOC, as both mineral-associated organic matter carbon (MAOM-C) and particulate organic matter carbon (POM-C), in four new perennial wheat genotypes (NPGs: 235 A, 280b, 11955 and OK72) after four years from planting. For indirect comparison, they were benchmarked against intermediate wheatgrass (Thinopyrum intermedium, IWG) and an annual durum wheat (Triticum durum). Across genotypes, SOC and MAOM-C varied strongly with depth and root trait expression. The highest SOC sequestration rate in the 0–40 cm layer was observed for 280b (1.76 Mg C ha⁻¹ yr⁻¹), followed by OK72 (1.45 Mg C ha−1 y−1), 11955 (1.33 Mg C ha−1 y−1) and 235 A (1.30 Mg C ha−1 y−1). The strongest genotype contrasts emerged across the full soil profile, particularly in subsoil MAOM-C stocks, where 280b, the line with the deepest and most developed root system, showed the highest cumulative value (72.91Mg C ha−1), and 235 A, the line with the least developed root system, the lowest (56.87 Mg C ha−1). Linear regression analyses identified architectural root traits as the most consistent predictors of SOC and MAOM stocks, with the strongest associations observed in the deeper soil layers (40–80 cm), highlighting the importance of a deep root system for stabilizing organic carbon at depth. These findings demonstrate that perenniality alone is insufficient to ensure durable SOC storage; instead, specific root trait syndromes control stabilization pathways. This trait-based framework provides operational indicators to guide carbon-oriented breeding aimed at maximizing long-term SOC sequestration in perennial grain systems.