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Abstract

Aegilops tauschii (Coss.) Schmal. (2n = 2x = 14, DD) (syn. A. squarrosa L.; Triticum tauschii) is well known as the D-genome donor of bread wheat (T. aestivum, 2n = 6x = 42, AABBDD). Because of conserved synteny, a high-density map of the A. tauschii genome will be useful for breeding and genetics within the tribe Triticeae which besides bread wheat also includes barley and rye. We have placed 249 new loci onto a high-density integrated cytological and genetic map of A. tauschii for a total of 732 loci making it one of the most extensive maps produced to date for the Triticeae species. Of the mapped loci, 160 are defense-related genes. The retrotransposon marker system recently developed for cultivated barley (Hordeum vulgare L.) was successfully applied to A. tauschii with the placement of 80 retrotransposon loci onto the map. A total of 50 microsatellite and ISSR loci were also added. Most of the retrotransposon loci, resistance (R), and defense-response (DR) genes are organized into clusters: retrotransposon clusters in the pericentromeric regions, R and DR gene clusters in distal/telomeric regions. Markers are non-randomly distributed with low density in the pericentromeric regions and marker clusters in the distal regions. A significant correlation between the physical density of markers (number of markers mapped to the chromosome segment/physical length of the same segment in microm) and recombination rate (genetic length of a chromosome segment/physical length of the same segment in microm) was demonstrated. Discrete regions of negative or positive interference (an excess or deficiency of crossovers in adjacent intervals relative to the expected rates on the assumption of no interference) was observed in most of the chromosomes. Surprisingly, pericentromeric regions showed negative interference. Islands with negative, positive and/or no interference were present in interstitial and distal regions. Most of the positive interference was restricted to the long arms. The model of chromosome structure and function in cereals with large genomes that emerges from these studies is discussed.

High-Density Linkage Mapping Revealed Suppression of Recombination at the Sex Determination Locus in Papaya

“…If chromosomal translocation had occurred, at least determination locus of papaya has not been previously reported in any centromeric clusters found in highhalf of the seeds derived from F 1 might not be viable (Klug and Cummings 1994). A seed germination test density maps of any other plant species (Davis et al 1994;Round et al 1997;Boyko et al 2002;Menz et al that we conducted (data not shown) failed to support the hypothesis that a translocation event was the basis 2002). Suppression of recombination in the papaya sex region is less likely the effect of the centromere and for the large linkage groups.…”

“…Sex-linked DNA markers. Four sequence-characterized amplified region (SCAR) markers tightly linked potato (Tanksley et al 1992;Haanstra et al 1999), wheat (Boyko et al 2002), soybean (Keim et al 1997, to sex forms were developed (Parasnis et al 2000;Deputy et al 2002;Urasaki et al 2002) as ways to and rapeseed (Lombard and Delourme 2001). sex the plant prior to flowering since known sexAmong the crop species, the genetic mapping of palinked vegetative characters are too far from the sexpaya lagged behind that of many other plant species, determining locus to be of practical use.…”

The Integration of Recombination and Physical Maps in a Large-Genome Monocot Using Haploid Genome Analysis in a Trihybrid Allium Population

“…20-30% of the chromosome arms in wheat (Gill et al 1996a,b;Akhunov et al 2003), barley (Pedersen et al 1995;Kü nzel et al 2000;Ste-DISCUSSION phens et al 2004), Aegilops tauschii (Boyko et al 2002), and maize (Tenaillon et al 2002; Koumbaris and Bass Most studies on the integration of physical and ge-2003; Anderson et al 2004). In this context it can be netic maps have been carried out using species in which hypothesized that this difference in recombination rate the construction of integrated maps was based on intraalong chromosomes is due to the difference in chromospecific recombination.…”

Using IRAP markers for analysis of genetic variability in populations of resource and rare species of plants

“…In this respect, LTR primers devel oped in related species for one of them can be used to amplify DNA of other species. Many more retrotrans posons have been detected in genomes of plants and animals, and therefore, the IRAP method has high potential for providing information (the number of loci and their polymorphism) [21,22]. New ret rotranspositions in the host genome may, depending on their location, lead to changes in gene activity, induce chromosomal alterations, dynamically affect chromosome sizes, and also promote recombination of chromosomes upon crossing over [4].…”