Investigation of Flowering Time in Barley: Exploiting Divergent Selection Between Spring and Winter European Cultivars

Spring and winter barley cultivars have adapted to contrasting environments through modification of both flowering time and cold acclimation pathways.  Therefore, genes underlying these pathways should display allelic variation between these two gene pools due to the strong influence of natural selection.  This research aims to test this prediction by investigating loci which are strongly differentiated between pools of Spring and Winter barley cultivars.   An F_ST analysis (measure of genetic differentiation) between Spring and Winter barley populations identified multiple regions that are diverged between the two populations.  Many of these regions correspond to well-characterised genes previously identified as components of Spring/Winter divergence. Other genomic regions correspond to locations only described as flowering time quantitative trait loci (QTL).  Comparison of the barley genome with the genomes of model grass species in which gene order is conserved was used to identify putative candidate flowering time genes in these regions.  Two candidate genes, which are orthologues of the Arabidopsis circadian clock genes LUX ARRHYTHMO (LUX) and CIRCADIAN1 (CIR1), were selected for validation and functional characterisation.  Both LUX and CIR1 are mutated in the early flowering barley near-isogenic mutant line BW284 and a population was developed to determine the genetic effects of these genes.  In addition to this work, exome capture and sequencing of spring and winter barley populations is being undertaken. This approach will be used to both evaluate our candidate gene approach and should give an improved and more comprehensive view of the effects of winter-spring divergent selection at a genome-wide level.