Two hundred sixteen barley (Hordeum vulgare L.) cultivars were
selected to represent the diversity and history of European spring
two-row barley breeding and to search for alleles controlling
agronomic traits by association genetics. The germplasm
was genotyped with 7864 gene-based single nucleotide
polymorphism markers and corresponding field trial trait data
relating to growth and straw strength were obtained at multiple
European sites. Analysis of the marker data by statistical
population genetics approaches revealed two important trends
in the genetic diversity of European two-row spring barley,
namely, i) directional selection for approximately 14% of total
genetic variation of the population in the last approximately 50
yr and ii) highly uneven genomic distribution of genetic diversity.
Association analysis of the phenotypic and genotypic data
identified multiple loci affecting the traits investigated, some of
which co-map with selected regions. Collectively, these data
show that the genetic makeup of European two-row spring barley
is evolving under breeder selection, with signs of extinction of
diversity in some genomic regions, suggesting that “breeding the
best with the best” is leading towards fixation of some breeder
targets. Nevertheless, modern germplasm also retains many
regions of high diversity, suggesting that site-specific genetic
approaches for allele identification and crop improvement such
as association genetics are likely to be successful.