## 4 Response of Barley to Abiotic Stresses
### Salinity
In addition, QTLs for days to heading, biomass, spike length, grain number per spike, 1000-seed weight, and K\({}^{+}\) content were discovered, all of which may be considered potential QTLs for breeding purposes. In another study, a set of 408 diversity arrays technology (DArT) markers were genotyped on 206 barley accessions from across the globe, and salt stress tolerance was assessed using the salinity tolerance score, a reliable characteristic created in prior research. A general linkage model (GLM) and a mixed linkage model (MLM) based on population structure and kinship were used to perform genome wide association analysis (GWAS) for salinity tolerance. In total, 24 significant marker-trait correlations discovered. In all techniques, a QTL on 4H with the closest marker of _bPb-9668_ was consistently observed [73]. Salinity stress tolerance was investigated in a DH population derived from the salinity resistant genotype CM72 and the salinity sensitive variety Gaidner, during the germination, seedling emergence, and first leaf full expansion development phases [74]. Deionized water and two NaCl treatments (150 mM and 300 mM NaCl) were used in the germination investigation. Three treatments were used to test salt tolerance in seedlings: control, and 150 mM NaCl injected during seedling emergence and the first leaf full expansion development phases. In this study, 12 QTLs on chromosomes 2H-6H were discovered, each accounting for 10-25% of the phenotypic variance. Fresh weight and dry weight per plant in salt stress during the first leaf full expansion development stage, as well as dry weight per plant in salt stress during seedling emergence, were associated with a QTL situated at 176.5 cM on chromosome 3H. On chromosome 2H, a persistent QTL for germination at both concentrations of salinity stress (150 and 300 mM NaCl) was found, although it was far away from the QTL connected to seedling stage salinity stress tolerance. [PERSON] et al. [75] tested an advanced backcross mapping population of barley in freshly reclaimed soil under two salinity levels of groundwater aquifers. A significant QTL linked with grain-weight-related features and the salt tolerance index (STI), which may be utilized to improve salinity tolerance, were found across the whole barley genome. Furthermore, the simple-sequence repeats (SSR) markers _bPb-3739_ (4H, 96.3 cM), _AF043094A_ (5H, 156 cM), _bPb-8161_ (7H, 2.22 cM), and _bPb-5260_ (7H, 115.6 cM) were the most significant genomic areas pertaining to vernalization, dwarfing, and dehydration genes, all of which are linked to salinity tolerance. A comparison of the Morex and Barke barley genomes revealed 436,640 InDels. [PERSON] et al. [76] generated 1140 InDel markers spanning the barley genome at an average genetic distance of 1 cM. A high-resolution melting (HRM) technique was used to genotype 55 InDel markers. The 1140 InDel markers were combined with 383 SSRs, 3909 gene-based SNPs, and 1544 DArT markers into a unified barley genetic map. In total, 6976 molecular markers (SSRs, DArTs, SNPs, and InDels) were combined into a single barley genetic map [76]. Quick map creation and gene fine-mapping will be enabled by HRM genotyping of InDel markers. In a European winter barley strain, the dynamic response of seedling development to varied degrees of salt stress and PEG6000-mediated osmotic stress was examined with 4885 gene-based SNP markers. A final collection of 56 phenotypic features was subjected to genome-wide association mapping, leading to the discovery of 28 quantitative trait loci (QTL), 10 of which were associated with saline environments and 20 were involved in osmotic stress [77]. More than one growth condition revealed four loci on chromosomes 1H, 5H, and 6H. However, under salt stress, one colocalized QTL was engaged in both root and shoot development. Based on their physical proximity to the QTL peak markers, a collection of prospective candidate genes with putative pleiotropic effects on seedling development under various circumstances is offered. [PERSON] et al.