Regulatory Mechanisms Underlying Stem Strength and Toughness in Dicotyledonous Plants: Implications for Soybean Breeding

Soybean (Glycine max) is a globally important crop valued for its high seed oil and protein content. However, lodging remains a major abiotic constraint that causes substantial yield losses. Lodging resistance is primarily determined by stem strength and toughness, which are governed by stem anatomical organization, vascular tissue development, and the composition and architecture of secondary cell walls (SCWs). This review synthesizes current knowledge on anatomical, structural, and genetic factors that are implicated in stem mechanical performance in dicotyledonous plants, with particular emphasis on vascular cambium activity, xylem and phloem differentiation, and the biosynthesis of major SCW components, including cellulose, hemicellulose, and lignin. These processes collectively determine stem rigidity, flexibility, and resistance to mechanical stress. By integrating insights from model species, especially Arabidopsis thaliana, and non-soybean dicots, this review highlights conserved regulatory pathways controlling stem development and SCW formation that are directly relevant to soybean improvement. The synthesis provides a translational framework for understanding how conserved anatomical and genetic mechanisms can be leveraged to enhance soybean stem strength, toughness, and lodging resistance. Overall, this review provides a conceptual foundation for future functional studies and breeding strategies to improve soybean yield stability and adaptability across diverse agronomic conditions.