Root angle, phosphorus, and water: Interactions and effects on durum wheat genotype performance in drought-prone environments

Abstract

Purpose: Selection for root traits has become a target in (pre-)breeding programs aiming at improving crop ability to capture soil resources. However, the benefit of selected traits in heterogeneous target environments will depend on spatial and temporal interactions between root systems, the soil environment (fertility and water supply) and management (fertiliser placement). Methods: We assessed growth and phosphorus acquisition of durum wheat (Triticum durum L.) lines defined by contrasting seminal root angles (41° ‘Narrow’ vs 82° ‘Wide’), in response to different soil phosphorus placements and seasonal water dynamics. Responses were evaluated in clear pots (seedlings), rhizoboxes (late-tillering stage) and a custom lysimeter system (flowering stage). Results: The Narrow genotype increased deep soil exploration (down to 50 cm) during early growth, with a tendency to more rapidly acquire phosphorus placed as a deep fertiliser band (25 cm depth). However, genotypic differences in shoot biomass or phosphorus uptake were not apparent at anthesis, in part due to phosphorus-induced changes in phenological development. Contrastingly, the wide genotype increased root growth in the topsoil (0–10 cm) when phosphorus was stratified in this layer and produced greater biomass at anthesis under these conditions. Shoot and root biomass and phosphorus uptake decreased when the topsoil dried out, with the greatest effect observed for phosphorus stratified in this layer. Conclusion: The benefits of the selected root angle trait strongly depend on nutrient and water distributions and dynamics in the target environment. Ideotype breeding efforts and farmer selection of genotypes should consider the context in which genotypes will be deployed. Highlight: The interaction between root system architecture and heterogeneous distributions of phosphorus and available water determine the relative performance of durum wheat genotypes with contrasting root angles.