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Title: Comparative genetic mapping in Fragaria virginiana reveals autosomal origin of sex chromosome

item SPIGLER, RACHEL - University Of Pittsburgh
item Lewers, Kimberly
item JOHNSON, ANNA - University Of Pittsburgh
item ASHMAN, TIA-LYNN - University Of Pittsburgh

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 5/26/2009
Publication Date: 5/31/2009
Citation: Spigler, R., Lewers, K.S., Johnson, A., Ashman, T. 2009. Comparative genetic mapping in Fragaria virginiana reveals autosomal origin of sex chromosome. Meeting Abstract.

Interpretive Summary:

Technical Abstract: Although most flowering plants are hermaphrodite, separate sexes (dioecy) have evolved repeatedly. The evolution of sex chromosomes from autosomes can often, but not always, accompany this transition. Thus, many have argued that plant genera that contain both hermaphroditic and dioecious members provide the unique opportunity to study the evolution of sexual systems as well as sex chromosomes. Species within these genera that exhibit intermediate sexual systems, such as subdioecy (hermaphrodites, females and males), in particular, can provide a portal to understanding the early stages of the transition of sex chromosomes from autosomes. Fragaria is such a genus, and Fragaria virginiana is such a species. Approximately twenty-five percent of the 22 species of Fragaria display some level of sexual polymorphism. While the vast majority of hermaphrodite species are diploid (N= 7), all of the sexually dimorphic species are the result of polyploid speciation events. Fragaria virginiana is an allopolyploid (N=28), with a sexual system that ranges from gynodioecy (females and hermaphrodites) to subdioecy. Scoring male and female sex functions as separate qualitative traits in a first generation genetic map revealed that sex function traits are on the same linkage group and are closely linked. With this in mind, we created a second generation SSR-based genetic map of Fragaria virginiana (Rosaceae). In doing so we are able to identify homeologous linkage groups in the octoploid and determine which of these houses the recently identified neo-sex chromosome. Moreover, we assessed the degree of chromosomal synteny by comparing our octoploid map to the published reference map of a diploid progenitor. This allowed us to identify the autosome that may correspond to the ancestor of the sex chromosome in Fragaria virginiana. This work represents some of the first to shed light on the evolutionary process that led to the formation of sex chromosomes in Fragaria, and lays the foundation for more intensive comparative genomics.