The Genetic Architecture of the Root System during Seedling Emergence in Populus euphratica under Salt Stress and Control Environments

The growth of the Populus euphratica root system is of great significance for its survival under adverse environmental stress. In harsh saline-stress environments, the proportion, morphology, and functionality of the taproots and lateral roots and how they manifest specific adaptive structures, growth strategies, and potential genetic controls are still subjects for further exploration. In this study, we delve into the fundamental patterns and trade-offs of root morphology and functionality by constructing an environment-induced differential interaction equation (EDIE) to model the independent and interactive growth of the root system while considering the influence of environmental conditions. We identify 93 key QTLs in the control group and 44 key QTLs in the salt-stress group, of which 2 QTLs are significant in both environments. By constructing ODE-based QTL networks, we explore in depth how these loci regulate the growth of the root system under different environmental conditions while considering their independent direct effects and epistatic effects among loci. This study elucidates the intrinsic factors that influence the variations in taproots and lateral roots, providing crucial insights into the relationship between root morphology and functionality.