Background: Barley (H. vulgare L.) is an important cereal crop cultivated across various climates globally. Barley and its ancestor (H. vulgare subsp. spontaneum) are an economically valuable model for genetic research and improvement. Drought, among various abiotic stresses, is a substantial threat to agriculture due to its unpredictable nature and significant impact on crop yield. Results: This study was conducted in both greenhouse and laboratory settings. Prior to the study, wild barley accessions were pre-selected based on their sensitivity or tolerance to drought as determined from fieldwork in the 2020–2021 and 2021–2022 cropping seasons. The effects of three levels of drought stress were evaluated (control, 90–95% field capacity [FC]; mild stress, 50–55% FC; and severe stress, 25–30% FC). Several parameters were assessed, including seedling and root growth, enzymatic activity (CAT, SOD, POD), soluble protein levels, chlorophyll content, carotenoids, abaxial and adaxial stomatal density and dimensions, and relative gene expression of Dhn1, SOD, POD, and CAT. Drought stress significantly increased enzyme activities, especially at 25–30% FC, and more in the tolerant genotype. On the other hand, sensitive genotypes showed a notable increase in stomatal density. Under drought stress, there was a general decline in seedling and root growth, protein content, chlorophyll and carotenoids, and stomatal dimensions. Importantly, gene expression analysis revealed that Dhn1, SOD, POD, and CAT were upregulated under drought, with the highest expression levels observed in the drought-tolerant genotype under severe stress conditions (25–30% FC). Conclusions: Our investigation highlights the distinct morphological, physiological, biochemical, and gene-expression profiles of drought-resistant and drought-sensitive wild barley genotypes under varying degrees of drought.

Potassium deficiency is one of the major issues affecting crop production around the globe. Giving the high cost of potassium fertilizers and environmental concerns related to inappropriate fertilization practices, developing more potassium use efficient (KUE) varieties is critical for sustainable food production in agricultural systems. In this study, we analysed the impact of potassium availability on agronomical attributes of thirty barley genotypes grown at four different levels of potassium (0.002 mM, 0.02 mM, 2 mM, 20 mM) under glasshouse conditions. The results showed that the availability of potassium in the soil had a major effect on yield components i.e., spike number, grain number and grain weight. Furthermore, grain weight showed a strong correlation with grain number and spike number at all levels of potassium supply. Although an increase in potassium supply led to an increase in plant height in all genotypes, the correlation with grain weight was very weak at all levels. Potassium supplementation caused an increase in shoot dry weight, which also showed a weak correlation with grain weight at the 0.002 mM potassium supply level. The genotypes Gebeina, Skiff, YF374, Flagship and YF374 were highly efficient in performing at suboptimal K supply levels and, thus, can be recommended to be grown in K-impoverished soils. We also suggest that grain and spike numbers could be used as proxies for KUE studies, to construct DH lines and identify QTL to improve low potassium tolerance and KUE in barley.

Hordeum spontaneum (wild barley) is a good gene source to improve salt tolerance in barley because it rapidly hybridizes and recombines with barley cultivars. Proteomics can assist in identifying proteins associated with a certain environmental or developmental signal. We employed a proteomic approach to understand the mechanisms of plant responses to salinity in a salt tolerant accession of H. spontaneum. At the 4-leaf stage, wild barley plants were exposed to 0 (control treatment) or 300 mM NaCl (salt treatment). The salt treatment lasted 3 weeks. Total proteins of leaf 4 were extracted and separated by two-dimensional gel electrophoresis. More than 500 protein spots were reproducibly detected. Of these, 29 spots showed significant differences between salt treatment and control. Using MALDI-TOF-TOF MS, we identified 29 cellular proteins, which represented 16 different proteins. These were classified into six categories and a group with unknown biological function. The proteins identified were involved in many different cellular functions. Three spots were identified as unknown proteins; searching in the NCBI database revealed that there was a 71% match with clathrin assembly protein putative [Ricinus communis], a 67% match with actin binding protein [Zea mays], and a 66% match with phosphatidylinositol kinase [Arabidopsis thaliana]. Other proteins identified included ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), oxygen-evolving enhancer protein (OEE), photosystem II reaction centerWprotein (Psbw), ribosomal proteins, chloroplast RNA binding protein (ChRBP), superoxide dismutase (SOD), malate dehydrogenase (MDH), thioredoxin h (Trx), nucleoside diphosphate kinase (NDPK), profilin, translationally-controlled tumor protein (TCTP), polyamine oxidase (PAO) and universal stress protein family (USP)