Physical Mapping Of Common Hexaploid Wheat 7DL Chromosome Arm With BAC Clones

Bread wheat (Triticum aestivum L.) is one of the most important crops worldwide. It is the most widely cultivated and consumed staple food crop. The availability of its complete genome can contribute to meeting the challenges of increasing food demand and the global climate change in the 21st century. However, wheat is an allohexaploid species (2n=6x=42) with the genome size of 17×109 bp/1C and 90% repetitive sequences, which makes it a daunting task to sequence and completely assemble its whole genome. The International Wheat Genome Sequencing Consortium (IWGSC) has initiated to map, sequence and assemble the wheat genome based on chromosome-by-chromosome approach.As part of the efforts of IWGSC, first of all, The long arm chromosome 7D were sorted from genetic materials by flowing cell. And 7DL specific BAC library was constructed using high weight molecular DNA. and this library is an essential tool for map based cloning of wheat important genes in 7DL. Then, we compared the SDS method with the plasmid DNA isolating kits, the results showed that SDS method is suit for isolating the BAC clone DNA and obtained the more DNA molecular. These improved experimental work offered the high quality DNA that provided a solid foundation for DNA digested analysis.We constructed a physical map for wheat (Chinese Spring) chromosome arm 7DL through fingerprinting 7DL-specific BAC clones by the high information content fingerprinting technique. A total of 50,304 clones (representing ca.15x equivalent of the chromosome arm) were fingerprinted, of which 43,486 clone-fingerprints were suitable for assembly. An automated assembly with the FPC software resulted in 1,614 contigs with 6,125 remained as singletons. The size of contigs N50 was 348kb; while L50310 contigs. A total of 4,457 clones for Minimum Tiling Path (MTP) were established during the physical map construction.The chromosomes and sequences of Aegilop tauschii is considered to share a high degree of similarity with the wheat D genome in respect of sequences and synteny as the former is the donor. Hence the physical map of Ae. tauschii could be helpful and convenient for the construction of wheat D chromosome physical map. We fingerprinted the long arm of wheat 7D BAC libraries, and then align the clones using the Ae. tauschii physical map as the template.845 contigs of wheat 7DL chromosome were anchored and ordered. The total length of anchored contigs to be 318Mb, and it reached 67.6% of 7DL total length.It is the first study to report the assembly and align BAC contigs of the wheat 7DL chromosome arms based on the physical map of Ae. tauschii. And our results demonstrates that aligning clones using the physical map of Ae. tauschii is an effective strategy for construction of physical maps for wheat D genome. It will accelerate the construction of physical maps of wheat 1-7D chromosomes, and pave the way for drawing the draft sequence of wheat D genome through BAC to BAC sequencing, subsequently it will accelerate to complete the whole genome of common hexaploid wheat.