A retrospective analysis of spring barley germplasm development from 'foundation genotypes' to currently successful cultivars

Twenty-eight mapped barley SSRs were used to examine changes in the level and pattern of variability in northern European spring barley over time. Comparing the most recently introduced cultivars with a group of 19 landraces and key progenitors termed 'foundation genotypes' we observed a reduction in the spectrum of alleles at 28 loci over time, and highlighted chromosomal regions with limited SSR allelic variation. The 19 'foundation genotypes' contained 72% of the alleles present in all the cultivars sampled. The smallest number of genotypes required to encompass all of the alleles detected in this study was 44, several of which were recently introduced cultivars. The level of diversity within modern cultivars was lower (0.484) than in the 'foundation genotypes' (0.597), although the values varied with the SSR locus. A total of 74 rare alleles (frequency <0.05) were detected in the cultivar sample, representing 34% of the total. Measures of genetic distance using SSRs, kinship coefficients and botanical descriptors were compared. Although the correlations between SSRs and kinship and SSRs and botanical descriptors were statistically significant (r = 0.26, p < 0.001 and r = 0.09, p < 0.001, respectively), SSR analysis provided greater resolution and allowed better discrimination between genotypes. Discussion of the results focuses on how this information can provide new opportunities in barley breeding.