Enhancing salinity tolerance in barley: harnessing introgressed nested genomes from the wild ancestor Hordeum spontaneum

Introgression of wild alleles from the wild progenitor (Hordeum vulgare subsp. spontaneum) of cultivated barley (Hordeum vulgare L.) provides a powerful approach to expand genetic variation and enhance abiotic stress resilience. However, potential of wild barley germplasm for improving salinity tolerance in cultivated barley has not yet been fully explored. In this study, 21 wild accessions from various geographical regions were crossed with the cultivated cultivar ‘Ryhan03’. Through backcrossing and successive selfing, a Nested Backcross Population (NBP) comprising 443 advanced lines was developed. All lines along with parents were evaluated under both saline and normal field conditions across two growing seasons. Salinity had a significant impact on most traits, leading to a 32% reduction in grain yield (GY). The results revealed that genome introgression between different wild genotypes (as the foreground) within the common background of cultivated barley generated significant genetic variation. Furthermore, a high rate of transgressive segregation was observed for the measured traits and salinity tolerance in advanced recombinant inbred lines (RILs), indicating the potential presence of beneficial alleles lost during domestication. Wild parents originating from Iraq, Iran, and Turkmenistan were identified as promising genetic resources for improving key traits, particularly salinity tolerance, in cultivated barley. Superior recombinant inbred lines (RILs) were identified under both salinity and normal conditions: lines 287, 24, 283, 247, 293, 281, 223, 176, 158, and 8 exhibited exceptional performance under salinity stress, while lines 117, 5, 4, 281, 187, 112, 354, 421, 204, and 297 excelled under normal conditions. Additionally, lines 287, 190, 247, 293, 88, 158, 212, 24, 31, and 40 achieved the highest scores for Yield Stability Index (YSI) and Selection Index of Ideal Genotype (SIIG) across both treatments, highlighting their potential for developing new barley varieties suited for both saline and non-saline environments. This study demonstrated that wild barley is a rich reservoir of beneficial alleles for improving salinity tolerance in cultivated barley using nested populations. Wild parents and superior lines with transgressive segregation were identified in both normal and saline environments.