Application of RH Mapping in Wheat Genome Analysis

Various biotic and abiotic factors for wheat production are posing big threat to feed the human population which is expected to be ~9 billion by 2050. These challenges have encouraged researchers to think of ways to utilize and develop resources to increase crop production and work is in progress to generate a gold standard reference wheat genome sequence. International Wheat Genome Sequencing Consortium established a chromosome-based strategy for developing physical maps and their eventual sequencing. About 2/3^rd length of any given wheat chromosome shows much reduced or nearly absent recombination events, and it makes ordering of a big proportion of the BAC contigs coming from low recombination region, almost impossible. Radiation Hybrid mapping offers a solution to precisely order the BAC contigs in low recombination regions of the wheat chromosomes. We constructed a whole genome RH panel and tested  its application for ordering BAC and NGS cotigs. Around 9000 SNP markers were grouped on wheat chromosomes and using a sequenced chromosome (3B) based comparison we showed that map resolution of ~300Kb can be achieved even in low recombination region. Our results indicated that RH mapping resource we developed will be highly useful to order physical maps of complex wheat genome to accelerate reference sequencing and subsequent map based cloning studies.