Stress-resilient dryland cereals: A review on mechanisms of drought and salinity tolerance

Millets and sorghum, considered as dryland cereals are particularly known for their capability to grow in adverse environments. The tolerance mechanisms to major abiotic stressors remain fragmented across physiological, biochemical and molecular studies. This review aims to scrutinise and synthesise the major tolerance mechanisms that millets perform under drought and saline stress. Published evidence on stress perception, physiological adjustment, biochemical defence and molecular regulation was reviewed and integrated. Drought tolerance mechanisms are primarily associated with osmotic adjustment, root system modification, osmoprotectant accumulation and stress-responsive signalling, which includes calcium-dependent protein kinases and mitogen-activated protein kinases. Salinity tolerance involves osmotic adjustment, ion homeostasis, the salt overly sensitive (SOS) pathway and microbe-mediated stress tolerance. Stress tolerance results from the coordinated maintenance of water status through physiological, biochemical and molecular processes. Importantly, high osmotic adjustment alone does not result in high productivity, whereas root development is important for sustained growth and yield. Rhizosphere interactions further contribute to alleviating stress by modifying plant water relations and ionic balance. The increasing demand for nutrient-dense crops, coupled with climate change-induced stress factors, necessitates the promotion of naturally stress-resistant plants to ensure food security and yield stability. Millets and sorghum exhibit resilience to various abiotic stresses, yet they remain underutilised due to limited awareness and cultivation efforts. This review highlights the need for functional gene validation, physiological-omics-based approaches and an understanding of the relationship between molecular responses and yield maintenance of crops under field stress to aid the development of climate-resilient dryland cereals.