SUMMARY: Developing climate‐resilient crops is critical for future food security and sustainable agriculture under current climate scenarios. Of specific importance are drought and soil salinity. Tolerance traits to these stresses are highly complex, and the progress in improving crop tolerance is too slow to cope with the growing demand in food production unless a major paradigm shift in crop breeding occurs. In this work, we combined bioinformatics and physiological approaches to compare some of the key traits that may differentiate between xerophytes (naturally drought‐tolerant plants) and mesophytes (to which the majority of the crops belong). We show that both xerophytes and salt‐tolerant mesophytes have a much larger number of copies in key gene families conferring some of the key traits related to plant osmotic adjustment, abscisic acid (ABA) sensing and signalling, and stomata development. We show that drought and salt‐tolerant species have (i) higher reliance on Na for osmotic adjustment via more diversified and efficient operation of Na⁺/H⁺ tonoplast exchangers (NHXs) and vacuolar H⁺‐ pyrophosphatase (VPPases); (ii) fewer and faster stomata; (iii) intrinsically lower ABA content; (iv) altered structure of pyrabactin resistance/pyrabactin resistance‐like (PYR/PYL) ABA receptors; and (v) higher number of gene copies for protein phosphatase 2C (PP2C) and sucrose non‐fermenting 1 (SNF1)‐related protein kinase 2/open stomata 1 (SnRK2/OST1) ABA signalling components. We also show that the past trends in crop breeding for Na⁺ exclusion to improve salinity stress tolerance are counterproductive and compromise their drought tolerance. Incorporating these genetic insights into breeding practices could pave the way for more drought‐tolerant and salt‐resistant crops, securing agricultural yields in an era of climate unpredictability.

Wheat is a major staple food in the human diet, but its production under current climate scenarios is problematic given the predicted extent of land salinization and the fact that wheat is highly sensitive to soil salinity. This work aims to critically assess previous breeding efforts and the pros and cons of targeting Salt Overly Sensitive 1 (SOS1) and High-affinity K+ Transporter 1 (HKT1) genes to improve salinity stress tolerance in wheat. We argue that overexpressing SOS1 genes encoding Na+/H+ exchangers for Na+ removal from root to the rhizosphere may come with the caveat of increased loading of Na+ into the xylem and its delivery to the shoot, as well as numerous pleiotropic effects. Similarly, targeting HKT1 transporters for removing Na+ from the shoot comes with significant yield penalties due to the high carbon cost of osmotic adjustment; this strategy is also limited by the relatively small capacity of the root to store excessive Na+ without experiencing toxicity symptoms. We suggest that targeting tissue tolerance traits such as K+ retention in mesophyll and vacuolar Na+ sequestration in the shoot will be able to deliver better outcomes. We also call for a better understanding of the structure–function relationships of various isoforms of key proteins involved in maintenance of Na+ and K+ homeostasis and a need for more in-depth physiological studies of wheat species with the DD genome, a key contributor to tissue tolerance traits. Our arguments are supported by a bioinformatic analysis of the number of orthologs for some key genes between hexaploid (AABBDD) and tetraploid (AABB) wheats and their structural differences.

Wild rice species provide a rich source of genetic diversity for possible introgression of salinity stress tolerance in cultivated rice. We investigated the physiological basis of salinity stress tolerance in Oryza species by using six rice genotypes (Oryza sativa L.) and four wild rice species. Three weeks of salinity treatment significantly (P < 0.05) reduced physiological and growth indices of all cultivated and wild rice lines. However, the impact of salinity-induced growth reduction differed substantially among accessions. Salt tolerant accessions showed better control over gas exchange properties, exhibited higher tissue tolerance, and retained higher potassium ion content despite higher sodium ion accumulation in leaves. Wild rice species showed relatively lower and steadier xylem sap sodium ion content over the period of 3 weeks analysed, suggesting better control over ionic sodium xylem loading and its delivery to shoots with efficient vacuolar sodium ion sequestration. Contrary to this, saline sensitive genotypes managed to avoid initial Na+ loading but failed to accomplish this in the long term and showed higher sap sodium ion content. Conclusively, our results suggest that wild rice genotypes have more efficient control over xylem sodium ion loading, rely on tissue tolerance mechanisms and allow for a rapid osmotic adjustment by using sodium ions as cheap osmoticum for osmoregulation.