title: Association mapping and the genomic consequences of selection in sunflower.
abstract: The combination of large-scale population genomic analyses and trait-based mapping approaches has the potential to provide novel insights into the evolutionary history and genome organization of crop plants. Here, we describe the detailed genotypic and phenotypic analysis of a sunflower (Helianthus annuus L.) association mapping population that captures nearly 90% of the allelic diversity present within the cultivated sunflower germplasm collection. We used these data to characterize overall patterns of genomic diversity and to perform association analyses on plant architecture (i.e., branching) and flowering time, successfully identifying numerous associations underlying these agronomically and evolutionarily important traits. Overall, we found variable levels of linkage disequilibrium (LD) across the genome. In general, islands of elevated LD correspond to genomic regions underlying traits that are known to have been targeted by selection during the evolution of cultivated sunflower. In many cases, these regions also showed significantly elevated levels of differentiation between the two major sunflower breeding groups, consistent with the occurrence of divergence due to strong selection. One of these regions, which harbors a major branching locus, spans a surprisingly long genetic interval (ca. 25 cM), indicating the occurrence of an extended selective sweep in an otherwise recombinogenic interval.
authors.affiliation: Department of Plant Biology, Miller Plant Sciences, University of Georgia, Athens, Georgia, United States of America.
authors.forename: Jennifer R
authors.initials: JR
authors.lastname: Mandel
authors.forename: Savithri
authors.initials: S
authors.lastname: Nambeesan
authors.forename: John E
authors.initials: JE
authors.lastname: Bowers
authors.forename: Laura F
authors.initials: LF
authors.lastname: Marek
authors.forename: Daniel
authors.initials: D
authors.lastname: Ebert
authors.forename: Loren H
authors.initials: LH
authors.lastname: Rieseberg
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Knapp
authors.forename: John M
authors.initials: JM
authors.lastname: Burke
mesh_terms: D002874:Chromosome Mapping; D056726:Genetic Association Studies; D014644:Genetic Variation; D018745:Genome, Plant; D006368:Helianthus / Q000235:genetics*; D006801:Humans; D015810:Linkage Disequilibrium; D010802:Phylogeny; D040641:Quantitative Trait Loci / Q000235:genetics*; D012641:Selection, Genetic
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