BAC-Based Sequencing of Bread Wheat Chromosome 6B and and its Application to the Study for the Region of Agronomic Importance

The International Wheat Genome Sequencing Consortium (IWGSC) makes efforts to obtain the high quality reference sequence of 17GB bread wheat genome.  As a part of the Japanese-funded “Genomics-based Technology for Agricultural Improvement” project, we are working to sequence the short (6BS) and long (6BL) arm of wheat chromosome 6B utilizing a minimum tiling path (MTP) BAC-by-BAC sequencing strategy.  Here we present our current status for the sequencing and assembling of chromosome 6B. 

We constructed the physical map covered 87% and 95% of short and long chromosome arms of 6B (6BS and 6BL), respectively, which were anchored to each arm using a radiation hybrid (RH) mapping.  Based on the physical map, we selected 3,936 and 4,608 BAC clones for 6BS and 6BL, respectively, and finally, BAC-by-BAC assembly was successfully completed for 7,573 BACs.  On average, 7.06 sequence contigs were assembled within one BAC clone.  To determine the orders and orientations of all assembled sequence contigs, we applied two mate-pair libraries (4Kb and 10Kb) from pooled BAC clones and obtained information for the scaffolds by SSPACE program.  We also mapped the wheat transcriptome data onto the sequences of chromosome 6B scaffolds to identify the information for genes and gene expression.  

A known region of wheat chromosome 6B related to the resistance against leaf rust has been projected onto the chromosome assembly to provide sequence-level information for further study.