Characterization of Barley Natural Variation At HvFT1 Locus Affecting Flowering Time.

The Flowering Locus T (FT1) is a central integrator of photoperiod and vernalization signals in the temperate cereals. As a mobile signal, FT1 facilitates the conversion of environmental cues received in the leaves to a plant reproductive response in the shoot apical meristem. In barley (Hordeum vulgare L.), natural variation in the promoter (9 linked SNPs and indels) and first intron (2 linked SNPs) of HvFT1 has been associated with large differences in flowering time. However, the specific effect of the different polymorphisms was previously unknown. In this study we took advantage of the identification of a new HvFT1 haplotype with a recombination event between the promoter and intron regions to dissect the effect of the promoter polymorphisms on flowering time. Using several separate segregating populations, we show that the two promoter haplotypes are associated with significant differences in flowering time in most populations and that those differences are independent of the haplotype present in the intron one region. The magnitude of these changes was modulated by the variation in other flowering genes and varied among populations. This study also discusses potential causes for different effects of seemingly identical alleles. The quantification of the effect of HvFT1 variation on flowering time is expected to give barley breeders a tool to engineer flowering time and improve adaptation of barley to changing environments.