The genetic potential of wild barley (Hordeum spontaneum C. Koch) to improve adaptation to low rainfall environments

A multi-faceted research study was conducted in an integrated approach encompassing field experiment, greenhouse test and molecular analysis on 57 barley lines carrying various levels of introgression from wild barley (Hordeum vulgare ssp. spontaneum) and 14 barley populations with contrasting response to drought stress. The main objective of this study was to examine the contribution of wild barley as a potential source of useful genes to the improved adaptation of germplasm developed by the ICARDA breeding program. A field experiment conducted on 57 barley introgression lines and 14 barley drought populations showed a considerable amount of genetic variability among the genotypes for the various agronomic and developmental traits measured in a range of Mediterranean environments. Traits such as early vigour, days to heading, peduncle length, plant height and thousand-kernel weight were important for yield improvement in the dry environments. The 57 introgression lines were genotyped using 74 SSR and 20 SNP markers for the analysis of graphical genotyping and LD based association mapping. The graphical genotyping analysis showed that the average length of donor chromosome segments of Hordeum vulgare ssp. spontaneum ranged between 20.3 and 45.4 cM for chromosomes 1H to 7H, with an overall average donor segment length of 35.0 cM. The association analysis revealed a total of 147 significant marker trait associations for grain yield and drought related traits. A total of 72 (49%) marker-trait associations showed favourable effects of the exotic germplasm where the Hordeum vulgare ssp. spontaneum lines contributed to an improvement of the trait under drought stress conditions. Marker-trait correlation analysis was done on the 14 drought populations using 50 SSR markers and the analysis revealed 51 significant (P Hordeum vulgare ssp. spontaneum background exhibited wide variation for vernalization and photoperiod responses while improved varieties from Australia and Ethiopia showed a narrow range of response to vernalization in both short and long-day photoperiods. The present study indicates that a combination of field, greenhouse and molecular studies could help in understanding the genetic mechanisms of drought tolerance in barley.