Comparison of wheat physical maps with barley linkage maps for group 7 chromosomes

Abstract

Comparative genetic maps among the Triticeae or Gramineae provide the possibility for combining the genetics, mapping information and molecular-marker resources between different species. Dense genetic linkage maps of wheat and barley, which have a common array of molecular markers, along with deletion-based chromosome maps of Triticum aestivum L. will facilitate the construction of an integrated molecular marker-based map for the Triticeae. A set of 21 cDNA and genomic DNA clones, which had previously been used to map barley chromosome 1 (7H), were used to physically map wheat chromosomes 7A, 7B and 7D. A comparative map was constructed to estimate the degree of linkage conservation and synteny of chromosome segments between the group 7 chromosomes of the two species. The results reveal extensive homoeologies between these chromosomes, and the first evidence for an interstitial inversion on the short arm of a barley chromosome compared to the wheat homoeologue has been obtained. In a cytogenetically-based physical map of group 7 chromosomes that contain restriction-fragment-length polymorphic DNA (RFLP) and random amplified polymorphic DNA (RAPD) markers, the marker density in the most distal third of the chromosome arms was two-times higher than in the proximal region. The recombination rate in the distal third of each arm appears to be 8-15 times greater than in the proximal third of each arm where recombination of wheat chromosomes is suppressed.

A Chromosome Bin Map of 2148 Expressed Sequence Tag Loci of Wheat Homoeologous Group 7

“…seven homoeologous groups of hexaploid wheat Kota et al 1993;Hohmann et al 1994Hohmann et al , 1995 Patterns of distribution and duplication of loci within and among the group 7 chromosomes of wheat and Delaney et al 1995a,b;Mickelson-Young et al 1995;Gill et al 1996a,b). Arm-specific physical maps and comparisons with rice and barley genomes were investigated.…”

“…2002). The physical maps of homoeologous group 6 and group 7 chromosomes and a comparative map of chromosomes 7 of wheat and barley (Hordeum vulgare MATERIALS AND METHODS L.) have been reported (Werner et al 1992;Hohmann et al 1995;Weng et al 2000). Landmark loci, which Genetic stocks: In this study various cytogenetic stocks of represent cDNA clones and single-or low-copy genomic the hexaploid wheat cultivar Chinese Spring (T. aestivum) DNAs that correspond to highly conserved coding rewere used.…”

“…All the genetic stocks selected for EST mapping were (Devos et al 1995;; Dubcovsky cytologically and/or molecularly verified by C-banding and et al 1996). Analyzing the degree of linkage conservaSouthern hybridization with Ͼ500 EST clones (Qi et al 2003). tion and synteny of chromosome segments between the EST singletons: The clones used in this study were develhomoeologous group 7 chromosomes of wheat and baroped from cDNA libraries of different tissues and developley, Hohmann et al (1995) identified extensive homolomental stages of wheat and other related species in the Triticeae tribe (Lazo et al 2004;Zhang et al 2004). The cDNA gies between these chromosomes.…”

“…Map construction: The group at North Dakota State UniverConsidering the homoeologous relationship between chromosomes of group 7 of wheat and barley, map positions of barley sity was responsible for analyzing the mapping data for homoeologous group 7 chromosomes (http:/ /wheat.pw.usda.gov/ chromosome 7 markers were compared to those of wheat group 7 markers (Kleinhofs et al 1993;Hohmann et al 1995). cgi-bin/westsql/map_locus.cgi).…”

“…The highest Distribution of loci and gene density: Physical RFLP maps produced using deletion stocks have been renumber of clones used in mapping the three homoeologous chromosome 7's was 111, and only 21 of these ported for each of the seven homoeologous chromosome groups and for some chromosome arms (Werner were cDNA probes (Hohmann et al 1995). A higher marker density was generally observed in et al 1992; Kota et al 1993;Hohmann et al 1994Hohmann et al , 1995 The loci presented here are those that were unambiguously assigned to each bin and not to the entire region, chromosome arm, or chromosome.…”