Abstract
BackgroundUnderstanding the evolution of cultivated barley is important for two reasons. First, the evolutionary relationships between different landraces might provide information on the spread and subsequent development of barley cultivation, including the adaptation of the crop to new environments and its response to human selection. Second, evolutionary information would enable landraces with similar traits but different genetic backgrounds to be identified, providing alternative strategies for the introduction of these traits into modern germplasm.ResultsThe evolutionary relationships between 651 barley landraces were inferred from the genotypes for 24 microsatellites. The landraces could be divided into nine populations, each with a different geographical distribution. Comparisons with ear row number, caryopsis structure, seasonal growth habit and flowering time revealed a degree of association between population structure and phenotype, and analysis of climate variables indicated that the landraces are adapted, at least to some extent, to their environment. Human selection and/or environmental adaptation may therefore have played a role in the origin and/or maintenance of one or more of the barley landrace populations. There was also evidence that at least some of the population structure derived from geographical partitioning set up during the initial spread of barley cultivation into Europe, or reflected the later introduction of novel varieties. In particular, three closely-related populations were made up almost entirely of plants with the daylength nonresponsive version of the photoperiod response gene PPD-H1, conferring adaptation to the long annual growth season of northern Europe. These three populations probably originated in the eastern Fertile Crescent and entered Europe after the initial spread of agriculture.ConclusionsThe discovery of population structure, combined with knowledge of associated phenotypes and environmental adaptations, enables a rational approach to identification of landraces that might be used as sources of germplasm for breeding programs. The population structure also enables hypotheses concerning the prehistoric spread and development of agriculture to be addressed.
Highlights
Understanding the evolution of cultivated barley is important for two reasons
polymorphism information contents (PIC) values varied between 0.05-0.90, in broad agreement with values previously obtained for Spanish barley landraces [9]
There were no significant differences between the overall diversities of two- and six-rowed barley landraces, though several individual microsatellites did show significant differences when these two sets of landraces were compared
Summary
Understanding the evolution of cultivated barley is important for two reasons. First, the evolutionary relationships between different landraces might provide information on the spread and subsequent development of barley cultivation, including the adaptation of the crop to new environments and its response to human selection. Many landraces died out during the last century, but seeds representing several thousand types from all parts of Europe are available from germplasm collections [5] These landrace collections are being looked on as important sources of germplasm with which to enrich the genepool of modern barley cultivars [6]. Exploitation of these landraces in modern crop breeding requires understanding of their phenotypic attributes and environmental adaptations, and their evolutionary relationships. This information would enable landraces with similar valuable traits but different genetic backgrounds to be identified, providing alternative strategies for the introduction of the traits into modern germplasm
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