Journal or Book Title
The Plant Genome
The small, annual grass Brachypodium distachyon (L.) Beauv., a close relative of wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.), is a powerful model system for cereals and bioenergy grasses. Genome-wide association studies (GWAS) of natural variation can elucidate the genetic basis of complex traits but have been so far limited in B. distachyon by the lack of large numbers of well-characterized and sufficiently diverse accessions. Here, we report on genotyping-by-sequencing (GBS) of 84 B. distachyon, seven B. hybridum, and three B. stacei accessions with diverse geographic origins including Albania, Armenia, Georgia, Italy, Spain, and Turkey. Over 90,000 high-quality single-nucleotide polymorphisms (SNPs) distributed across the Bd21 reference genome were identified. Our results confirm the hybrid nature of the B. hybridum genome, which appears as a mosaic of B. distachyon-like and B. stacei-like sequences. Analysis of more than 50,000 SNPs for the B. distachyon accessions revealed three distinct, genetically defined populations. Surprisingly, these genomic profiles are associated with differences in flowering time rather than with broad geographic origin. High levels of differentiation in loci associated with floral development support the differences in flowering phenology between B. distachyon populations. Genome-wide association studies combining genotypic and phenotypic data also suggest the presence of one or more photoperiodism, circadian clock, and vernalization genes in loci associated with flowering time variation within B. distachyon populations. Our characterization elucidates genes underlying population differences, expands the germplasm resources available for Brachypodium, and illustrates the feasibility and limitations of GWAS in this model grass.
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This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.
UMass SOAR Fund. This material is based on work supported by the National Institute of Food and Agriculture (NIFA), USDA, the Massachusetts Agricultural Experiment Station, and the Biology Department of the University of Massachusetts–Amherst under project number MAS00419 to A.L.C. and S.P.H., and the Office of Science (BER) Department of Energy Grant DE-SC0006621 to S.P.H.
Tyler, Ludmila; Lee, Scott J.; Young, Nelson D.; Delulio, Gregory A.; Benavente, Elena; Reagon, Michael; Sysopha, Jessica; Baldini, Riccardo M.; Troìa, Angelo; Hazen, Samuel P.; and Caicedo, Ana L., "Population Structure in the Model Grass Brachypodium distachyon Is Highly Correlated with Flowering Differences across Broad Geographic Areas" (2016). The Plant Genome. 622.