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

在系统发育的时间尺度上，植物驯化是最近才发生的。因此，农作物常常与它们的野生祖先发生干涉性。在野生植物和驯化植物共存的地区，可以发生杂交。如果作物-野生基因流动——无论从哪个方向——都能带来适应性方面的好处，它就会产生杂交群体，例如，在野生背景下，这些群体拥有来自作物渗入者的有益等位基因。大麦（Hordeum vulgare L.）是一种重要的作物物种，其驯化过程在考古学、遗传学和分子水平上都得到了广泛的研究。在过去的几十年里，植物学家观察到“六棱野生大麦”，即野生大麦在每个花序节上有三个可育的小花，这是驯化大麦的一个显著特征。有几种途径可以产生这些中间形式：(i)野生型和驯化型之间的杂交；（ii）驯化基因的从头突变；（iii）通过基因重组去驯化。我们对以色列三个六棱野生大麦群体的初步序列数据支持在其他野生基因组背景下存在显示驯化单倍型的杂交群体，并提出了驯化六棱穗（Vrs1）等位基因自适应渗进杂草野生大麦的假设。为了验证这一假设，我们将进行以下实验和分析：(i)对以色列新采集的六棱野生大麦和同域的二棱基因型进行群体基因组分析，以检测作物-野生基因流的基因组足迹；（ii）通过生态生理实验来了解杂草大麦六排表型的适合度结果；(3)对实验群体中与杂草有关的性状进行遗传作图，以确定野生植物适应农业环境的遗传因素。利用经过充分研究的植物驯化模型，我们的研究将揭示帮助野生植物在人造栖息地茁壮成长的适应过程。

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.