Assessment of genetic diversity among Jordanian wild barley (Hordeum spontaneum) genotypes revealed by SSR markers

Wild barley, Hordeum spontaneum is the progenitor of cultivated barley. The center of diversity is in the Fertile Crescent in the Near East, where wild barley grows under a wide range of environmental and climatic conditions. Jordan wild barley is expected to harbor important genes that could be used for the improvement of the cultivated varieties especially in their tolerance to drought. To assess genetic diversity and allelic variation of Jordanian wild barley, 103 wild barley genotypes collected from different parts of Jordan along with 29 cultivated barley genotypes were analyzed for diversity by means of Simple Sequence Repeats (SSR). The spontaneum genotypes were grouped into six populations according to their longitude, latitude, altitude, and rainfall zone of the sites from where they have been collected, and the cultivated in one population. All barley genotypes were analyzed with 11 SSR markers with known sequences and chromosomal locations. The 11 microsatellite markers revealed 237 alleles, with an average of 21.5 alleles per locus. In spontaneum genotypes, 209 alleles were identified with an average of 19 alleles per locus, whereas, cultivated genotypes had 95 alleles with an average of 8.6 alleles per locus. Moreover, 52 alleles were identified in spontaneum (22 %) of the total alleles and 22 alleles in cultivated barley (9 %). The level of genetic diversity was very high; in fact, mean in total gene diversity (Ht) was 0.86 ranging from 0.72 to 0.94. Average gene diversity (H) was 0.79 ranging from 0.74 to 0.82. Genetic variation within population was much higher than among populations at molecular levels: this was also supported by the finding that morphological characters such as awn length, plant height, days to maturity, peduncle length, peduncle extrusion and tillering number, showed higher variation within populations than among populations. Clustering of populations was according to their ecological geographical pattern.