Adaptive introgression in hybrid swarms between wild and domesticated barley in Israel

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Plant domestication has occurred very recently on a phylogenetic timescale. Hence, crop plants are often interfertile with their wild progenitors. In regions, where wild and domesticated plants co-occur, hybridization can happen. If crop-wild geneflow – in either direction – confers fitness benefits, it can give rise to hybrid swarms that harbor, for instance, in a wild background beneficial alleles donated from a crop introgressor. Barley (Hordeum vulgare L.) is an important crop species, whose domestication process has been intensely studied at the archaeological, genetic and molecular level. In past decades, botanists have observed “six-rowed wild barley”, i.e. wild-growing barley showing three fertile florets per inflorescence node, a hallmark trait of domesticated barley. There are several avenues to bring about these intermediate forms: (i) hybridization between wild and domesticated types; (ii) de novo mutation of domestication genes; (iii) de-domestication by genetic recombination. Our preliminary sequence data of three six-rowed wild barley populations in Israel support the presence of hybrid swarms showing domesticated haplotypes in an otherwise wild genomic background, and motivate the hypothesis of adaptive introgression of domesticated SIX ROWED SPIKE (Vrs1) alleles into weedy wild barley. To test this hypothesis, we will conduct the following experiments and analyses: (i) population genomic analyses of newly collected six-rowed wild barleys from Israel and sympatric two-rowed genotypes to detect genomic footprints of crop-wild gene-flow; (ii) eco-physiological experiments to understand the fitness consequence of a six-rowed phenotype in weedy barley; and (iii) genetic mapping of traits associated with weediness in experimental populations to identify genetic factors involved in adaptation of wild plants to agricultural environment. Taking advantage of a well-studied model of plant domestication amenable to genetic studies, our research will shed light on adaptation processes that help wild plants thrive in man-made habitats.