Developing an Original Theoretical Framework for Root Architecture Optimisation in Drought-Prone Sorghum Production Systems of the Sahel Savanna

Root architecture determines a crop's capacity to explore soil water and nutrient reserves, and developing an original theoretical framework that integrates root system ideotype design with soil water availability modelling for sorghum in the Sahel savanna represents a significant contribution to crop physiology and breeding theory. This study developed an original theoretical framework for root architecture optimisation in sorghum under Sahel savanna drought conditions, with empirical grounding in the production zones of Borno and Yobe States. A multi-phase theory-building methodology was employed: systematic review of root architecture theory for cereals (64 publications from 2018 to 2024), functional structural plant modelling using FSPM-Wheat adapted for sorghum root architecture, empirical root phenotyping of 24 sorghum genotypes at three soil water levels using shovelomics and digital imaging at Maiduguri Experimental Station, and expert consultation with 18 root physiology and sorghum breeding specialists. The review identified significant gaps in integrating soil texture heterogeneity of Sahel soils into root architecture optimisation models. Phenotyping confirmed significant genetic variation in root angle (38 to 71 degrees from vertical), root number per nodal whorl (4.8 to 11.3), and lateral root density (1.2 to 4.7 per cm primary root). The original Root Architecture Optimisation Framework (RAOF) for Sahel sorghum proposes that drought-adaptive root ideotypes should combine steep crown root angle for subsoil water access, high root hair density for P acquisition from shallow horizons, and moderate lateral density to balance exploration and construction costs.