The development and characterisation of a bacterial artificial chromosome library for Fragaria vesca

A BAC library, consisting of 18,432 clones was constructed from Fragaria vesca f. semperflorens accession 'Ali Baba'. BAC DNA from individual library clones was pooled to create a PCR-based screening assay for the library, whereby individual clones could be identified with just 34 PCR reactions. These pools were used to screen the BAC library and anchor individual clones to the diploid Fragaria reference map (FV×FN).Clones from the BAC library developed contained an average insert size of 85 kb, representing over seven genome equivalents. The pools and superpools developed were used to identify a set of BAC clones containing 70 molecular markers previously mapped to the diploid Fragaria FV×FN reference map. The number of positive colonies identified for each marker suggests the library represents between 4× and 10× coverage of the diploid Fragaria genome, which is in accordance with the estimate of library coverage based on average insert size.This BAC library will be used for the construction of a physical map for F. vesca and the superpools will permit physical anchoring of molecular markers using PCR.The strawberry species Fragaria ×ananassa is a member of the Rosaceae, and is one of the most economically-important soft-fruit species. However, it is an allo-octoploid species (2n = 8x = 56), which grants it genetically complex status. Fragaria vesca is a diploid (2n = 2x = 14) relative of the cultivated strawberry, that has been demonstrated to be the closest extant diploid to the ancestor of the cultivated octoploid strawberry [1,2]. F. vesca has a genome size of approximately 206 Mb/C [3], a short reproductive cycle and facile vegetative and seed propagation, as well as amenability to genetic transformation. These features make it an ideal model organism for forward and reverse genetics studies in Fragaria.There currently exists a well characterised, saturated genetic linkage map for diploid Fragaria developed from an interspecific cross between F. vesca and ano