Breeding for Resilient Cereals: Integrating Molecular Networks and Trait-Based Selection to Improve Nitrogen and Water Use Efficiencies.

Cereal crops are fundamental to global food security, but their production is increasingly challenged by rising demand and the unpredictable impacts of climate change. Among the most limiting and interdependent resources sustaining yields are nitrogen and water. Improving nitrogen and water use efficiencies is therefore essential for sustainable agricultural production. This review examines the relationship between nitrogen use efficiency (NUE) and water use efficiency (WUE) in cereal crops, highlighting how progress in one trait can influence the other. We provide an overview of the physiological and molecular mechanisms that regulate NUE and WUE and discuss how these pathways are interconnected. By comparing key genes across major cereals, we explore how plants balance nitrogen and water acquisition under simultaneous stress. The review further considers below- and above-ground morphological traits and advances in biotechnology aimed at enhancing both efficiencies. We synthesize current knowledge into a conceptual framework for breeding resilient cereal cultivars, including a cross-tolerance network model and breeding strategies that integrate physiological, molecular, and morphological insights. This review provides a foundation for developing cereals adapted to water- and nitrogen-limited environments.