Date: Saturday, January 14, 2012
Time: 8:40 AM
Time: 8:40 AM
Room: Town and Country
Genome sequencing of the ≈17 Gb wheat genome is complicated by its size and repetitive nature. Physical maps are essential for efficient sequence assembly. To develop physical maps of all seven D-genome chromosomes of wheat, we are using radiation hybrid mapping which relies on random radiation-induced breakage to calculate marker order. In this presentation we report on our progress to develop RH map of all D-genome chromosomes of wheat. Several protocols were used to generate RH maps of various resolutions. Here we report a quick, high throughput, and cost-effective approach based on pollen irradiation. Endosperm samples derived from pollen irradiation using variable dosages were generated and compared for marker retention rates. An 81-member subset of 2.0-krad treatment lines was assayed using molecular markers. We constructed RH maps for all 7 D-genome chromosomes incorporating 967 markers. Total map distances for chromosomes 3D and 7D were 1819.7 cR2000 and 2408.0 cR2000, respectively. A comparison of the cM/ cR2000 ratio of chromosomes 3D and 7D produced ratios of 1:15 and 1:13, respectively. Marker orders were comparable to previously reported genetic maps. The average mapping resolution was calculated as ~685 kb. Map resolution was validated using markers from sequenced contigs of chromosomes 3B and 3D. Analysis of deletion patterns induced by γ radiation indicated several interstitial deletions per chromosome per line while ~33% of deletions were 1 to 20 Mb in size. High throughput genotyping platforms are now being utilized to generate complete D-genome physical maps with ~20,000 marker loci needed for adequate coverage.