Genetic Diversity in 19th Century Barley (Hordeum vulgare) Reflects Differing Agricultural Practices and Seed Trade in Jämtland, Sweden

Landrace crops are important genetic resources, both for plant breeding efforts and for studying agrarian history. The distribution of genetic diversity among landraces can reflect effects of climate, economic structure, and trade also over a limited spatial and temporal scale. In this study, we have SNP genotyped historical barley seed samples from the late 19th century, together with extant barley landrace accessions from Jamtland, Sweden, a county centrally located, situated between Sweden and Norway. We found two main genetic clusters, one associated with the main agricultural district around lake Storsjon and one in the peripheral areas. Data was also compared with genotypes from landraces from across the Scandinavian peninsula. Accessions from the peripheral part of Jamtland show genetic similarity to accessions from a large part of central Scandinavia, while the accessions from the Storsjon district are more differentiated. We suggest that these dissimilarities in genetic diversity distribution are explained by differences in the relative importance of agriculture and trading. We further compared the historical material with ex situ preserved extant landraces from the same region and found that their genetic diversity was not always representative of the given provenience. The historical material, in contrast, proved particularly valuable for assessing how crop genetic diversity has historically been influenced by economic focus.