Drought stress can occur at any growth stage and can affect crop productivity, which can result in large yield losses all over the world. In this respect, understanding the genetic architecture of agronomic traits under drought stress is essential for increasing crop yield potential and harvest. Barley is considered the most abiotic stress-tolerant cereal, particularly with respect to drought. In the present study, worldwide spring barley accessions were exposed to drought stress beginning from the early reproductive stage with 35% field capacity under field conditions. Drought stress had significantly reduced the agronomic and yield-related traits such as spike length, awn length, spikelet per spike, grains per spike and thousand kernel weight. To unravel the genetic factors underlying drought tolerance at the early reproductive stage, genome-wide association scan (GWAS) was performed using 121 spring barley accessions and a 9K single nucleotide polymorphisms (SNPs) chip. A total number of 101 significant SNPs, distributed over all seven barley chromosomes, were found to be highly associated with the studied traits, of which five genomic regions were associated with candidate genes at chromosomes 2 and 3. On chromosome 2H, the region between 6469300693-647258342 bp includes two candidate drought-specific genes (HORVU2Hr1G091030 and HORVU2Hr1G091170), which are highly associated with spikelet and final grain number per spike under drought stress conditions. Interestingly, the gene expression profile shows that the candidate genes were highly expressed in spikelet, grain, spike and leaf organs, demonstrating their pivotal role in drought tolerance. To the best of our knowledge, we reported the first detailed study that used GWAS with bioinformatic analyses to define the causative alleles and putative candidate genes underlying grain yield-related traits under field drought conditions in diverse barley germplasm. The identified alleles and candidate genes represent valuable resources for future functional characterization towards the enhancement of barley cultivars for drought tolerance.

The response of Peganum harmala L. seedlings subjected to salinity was investigated through the observation of germination at the 4th, 6th and 8th days under normal and two salinity levels (150 and 200 mM NaCl). Genetic response of P. harmala was examined by quantitative estimation and electrophoretic separation of catalase and salt-soluble proteins. The gene expression of catalase and osmotin were investigated using RT-PCR. Final percentage of germination at the eighth day of germination was reduced from 85% in the control to 70 and 30% under the concentration of 150 and 200 mM. The catalase activity and protein content increased as the salinity increased compared to control seedlings. The electrophoretic separation of catalase and salt-soluble proteins exhibited stress-related isozymes and protein bands. RT-PCR of cat1, cat2-3 and cat3 and osmotin genes exhibited up-regulation and down-regulation of genes subsequent to salinity. The reduced germination percentage of salt stressed seedlings was attributed to oxidative damage and osmotic imbalance. The increased catalase activity and protein content were concluded as protective response of P. harmala seedlings to salinity induced oxidative stress and osmoregulation. The additional isozyme bands in the salt-stressed seedlings indicated modulation of CAT gene expression in response to elevated H2O2 subsequent to salinity. The stress specific gene expression was interpreted as molecular mechanism by which plants can tolerate salinity stress. The up-regulation of cat2-3 gene in relation to stress suggests it crucial role in salinity tolerance in P. harmala and further studies are needed for its sequence identification.

Salinity represents a major constraint on plant development and crop productivity in wheat, which represents one of the most critical sources of dietary calories worldwide. Its detrimental effects are particularly pronounced during the early stages of growth, including seed germination and seedling establishment. Salinity tolerance is a multifaceted trait governed by several interrelated mechanisms, notably ion homeostasis, osmotic adjustment, activation of enzymatic antioxidant systems, and transcriptional regulation of ion transporter genes. In the present study, contrasting wheat genotypes exhibiting differential salinity tolerance were selected from a panel of 172 accessions evaluated under salinity stress (175 mM NaCl) and control conditions (0 mM NaCl). The objectives of the current study are to confirm the underlying physiological and molecular mechanisms conferring salinity tolerance. Key physiological and molecular parameters including Na⁺, K⁺, and P homeostasis; activities of major antioxidant enzymes; and expression profiles of the salinity-responsive ion transporter genes TaAVP1 and NHX1 were quantified in six tolerant genotypes and one susceptible genotype. The tolerant genotypes exhibited higher concentrations of Na⁺ and K⁺ and elevated activities of all antioxidant enzymes, compared with the susceptible genotype. Furthermore, the tolerant genotypes showed differential expression of TaAVP1 and NHX1: both genes were upregulated in Javelin 48 and Kandahar, whereas they were downregulated in genotype 1018d. Notably, genotype Kule demonstrated the highest Na⁺ accumulation, accompanied by markedly elevated activities of all major antioxidant enzymes, with ascorbate peroxidase and glutathione reductase increasing by 9.20-fold and 2.32-fold, respectively, under salinity stress. Based on these findings, the tolerant genotypes can be categorized into two functional groups: Javelin 48, Ghati, and 1018d (characterized by high K⁺ and salinity tolerance) are better suited to soils affected by low Na⁺ salinity, whereas Kandahar, Kule, and 1049 (characterized by high Na⁺ and sodicity tolerance) are more adapted to soils with elevated Na⁺ levels. In conclusion, the tolerant genotypes exhibited distinct, coordinated mechanisms to mitigate salinity stress, underscoring the complexity and plasticity of adaptive responses in wheat.