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GrainGenes Reference Report: PMB-48-767

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Reference	PMB-48-767
Title	A high-density cytogenetic map of the Aegilops tauschii genome incorporating retrotransposons and defense-related genes: insights into cereal chromosome structure and function
Journal	Plant Molecular Biology
Year	2002
Volume	48
Pages	767-790
Author	Boyko E [ Show all 7 ]
Abstract	Summary: 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 micrometer) and recombination rate (genetic length of a chromosome segment/physical length of the same segment in micrometer) 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
Keyword	[ Hide all but 1 of 75 ] 50 80 aegilops aegilops tauschii arms bare-1 retrotransposon barley bread bread wheat breeding cereal chromosome chromosome chromosome structure cluster conserved synteny correlation coss cultivated barley d genome d-genome donor date defense response defense-related gene defense-related genes deficiency density disease resistance genes fragment length polymorphism function gene gene cluster gene-cluster genetic map genome high-density hordeum hordeum vulgare interference interval island islands issr linkage map locus long arm map marker microsatellite model molecular genetic map negative and positive interference pericentromeric regions phaseolus vulgaris physical maps placement rate recombination region resistance resistance and defense-response genes retrotransposon retrotransposons rich regions rye segment squarrosa structure synteny system tauschii tribe triticeae triticum triticum tauschii wheat triticum-aestivum

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