Development of genomic resources for Fragaria iinumae: a second diploid ancestor to the octoploid cultivated strawberry

The cultivated strawberry, Fragaria x ananassa, and its immediate ancestors F. chiloensis and F. virginiana, are octoploids (2n=8x=56). The subgenome compositions of these octoploid species have yet to be fully determined. An abundance of evidence indicates that at least one of the octoploids’ subgenomes is derived from a diploid ancestor that resembles contemporary diploid Fragaria vesca. On this basis, the strawberry genomics community has adopted F. vesca as a model species. Transformation systems and linkage maps have been developed for it, and the genomic sequence of F. vesca subsp. vesca “Hawaii 4” was published in early 2011. In recent years, phylogenetic and other evidence has accumulated implicating another diploid species, F. iinumae, as a second subgenome contributor to the octoploid strawberries. Intriguingly, a mitochondrial marker is shared uniquely between F. iinumae and all octoploids examined, suggesting that F. iinumae may be the source of the octoploids’ mitochondrial genome. We are developing germplasm and genomic resources for F. iinumae, including high throughput genomic sequence data, molecular markers, and the first F. iinumae linkage mapping population. This map is based on segregation data from an F2 population of 150 seedlings derived from a cross two F. iinumae accessions collected in Hokkaido, Japan by Tom Davis and Kim Hummer in 2004. The status of knowledge and resource development in F. iinumae will be described.