Genomic resources and physical mapping of the B. rapa genome

Abstract

The genus Brassica includes the most extensively cultivated dicotyledonous vegetable crops worldwide. Investigation of the Brassica genome presents excellent challenges to study plant genome evolution and divergence of gene function associated with polyploidy and genome hybridization. Among the Brassica crops, Brassica rapa has been an ideal model for genomic studies on the Brassica species. B. rapa (AA genome) has a relatively compact diploid genome (529 Mb), compared to Brassica nigra (BB genome, 632 Mb) and Brassica oleracea (CC genome, 696 Mb). There is also a large collection of cultivars and a broad array of available genomic resources including five large-insert bacterial artificial chromosome (BAC) libraries providing 53-fold genome coverage, end sequences of approximately 146,000 BAC clones, > 150,000 ESTs from 33 cDNA libraries, successful shotgun sequencing of 886 euchromatic region-tiling BACs, and a BAC-based physical map. These genomic resources provided fundamental basis of the genome sequencing project and contributed to successful assembly of the whole genome sequences.