Comparison of genetic and physical maps of group 7 chromosomes from Triticum aestivum L.

Abstract

We present a high density physical map of homoeologous group 7 chromosomes from Triticum aestivum L. using a series of 54 deletion lines, 6 random amplified polymorphic DNA (RAPD) markers and 91 cDNA or genomic DNA clones from wheat, barley and oat. So far, 51 chromosome segments have been distinguished by molecular markers, and 54 homoeoloci have been allocated among chromosomes 7A, 7B and 7D. The linear order of molecular markers along the chromosomes is almost identical in the A- B- and D-genome of wheat. In addition, there is colinearity between the physical and genetic maps of chromosomes 7A, 7B and 7D from T. aestivum, indicating gene synteny among the Triticeae. However, comparison of the physical map of chromosome 7D from T. aestivum with the genetic map from Triticum tauschii some markers have been shown to be physically allocated with distortion in more distal chromosome regions. The integration of genetic and physical maps could assist in estimating the frequency and distribution of recombination in defined regions along the chromosome. Physical distance did not correlate with genetic distance. A dense map facilitates the detection of multiple rearrangements. We present the first evidence for an interstitial inversion either on chromosome arm 7AS or 7DS of Chinese Spring. Molecularly tagged chromosome regions (MTCRs) provide landmarks for long-range mapping of DNA fragments.

Genetic mapping of 66 new microsatellite (SSR) loci in bread wheat

“…Despite this, detailed RFLP genetic maps with more than 1,500 mapped loci spanning a genetic distance of over 3,700 cM (a density of 4.4 Mb per cM) are now available for bread wheat, due to concerted efforts made by several laboratories, coordinated by the ITMI (see Communicated by P. Langridge Gupta et al 1999 for a review). Physical maps for all 21 chromosomes involving a sizable proportion of the genetically mapped loci are also available Kota et al 1993;Hohmann et al 1994;Ogihara et al 1994;Delaney et al 1995a, b;Mickelson-Young et al 1995;Varshney et al 2001). These genetic and physical maps, however, are still far from the ultimate objective of getting a map as saturated as those available for the tomato and rice genomes.…”

High-Resolution Radiation Hybrid Map of Wheat Chromosome 1D

“…durum L. 2n ¼ 4x ¼ 28; A and B genomes) have multiple genomes with chromosomes characterized by regions differing in gene density and distribution (Gill et al 1993(Gill et al , 1996aHohmann et al 1994;Delaney et al 1995a,b;Sandhu and Gill 2002). Eighty percent of the wheat genome is composed of repetitive sequences (Smith and Flavell 1975).…”

“…However, the overall relationship between gene density and relative position on the chromosome is weak (Akhunov et al 2003). As in many plant species, recombination along chromosome arms in wheat is not evenly distributed, being absent in proximal regions of all arms (Gill et al 1993;Lukaszewski and Curtis 1993;Hohmann et al 1994;Delaney et al 1995a,b;Endo and Gill 1996;Sandhu and Gill 2002). Recombination rate increases with approximately the square of the relative distance of a given segment from the centromere (Akhunov et al 2003).…”

Introgression mapping in the grasses. I. Introgression of Festuca pratensis chromosomes and chromosome segments into Lolium perenne

“…These include in situ hybridization of single-copy probes (Chen & Gustafson, 1995) and the analysis of deletion lines defined by C-banding (Gill et al, 1993;Hohmann et al, 1994;. Potentially, the Lp/Fp introgression mapping system has important advantages over these methods.…”