In this study genetic diversity of cultivated and wild barley under drought stress conditions were evaluated. Then the effect of introgressed chromosomal segments of Hordeum vulgare . spontaneum (HSP) in the cultivated background, and differences in sequence of chromosomal regions containing genes related to drought stress in tolerant and susceptible barley cultivars were assessed. Agronomic, morphological and physiological traits were studied in the field under three water environments during 2 years. The 21 diverse HSP genotypes selected were crossed with Reihan 03 cultivar and 443 BC1F2 lines were generated. Also 102 BC2F2 lines were generated from one of the crosses. These lines were evaluated for agronomic traits under 3 water environments. Finally a bacterial artificial chromosome (BAC) library was constructed for Reihan 03 cultivar and screened for HvDREB1 and HvWRKY1 genes, which have well-known role in drought tolerance. The HSP genotypes had lower yield potential, but higher yield stability under water stress condition, as well as more extensive (weight, length, area and volume) root system compared to the cultivated ones. High genetic diversity in BC1F2 and BC2F2 populations indicated that a high portion of genetic diversity of HSP is introgressed in the genetic background of Reihan 03. Transgressive segregation was observed for agronomic traits in most of the crosses and some lines with favorable characteristics and high drought tolerance were identified. High differences in DNA sequence was observed in the cloned regions between tolerant (Reihan 03) and susceptible (Morex) cultivars. Some of the in the genes caused differences in amino acid sequence or deletion in parts of the amino acid sequence. Key words: wild genome, transgressive segregation, BAC library,, Multi-parent populations
