A chromosome bin map of 2148 expressed sequence tag loci of wheat homeologous group 7. Genetics

Department of Plant Sciences, North Dakota State University, Fargo, North Dakota 58105, USA.
Genetics (Impact Factor: 5.96). 10/2004; 168(2):687-99. DOI: 10.1534/genetics.104.034850
Source: PubMed


The objectives of this study were to develop a high-density chromosome bin map of homoeologous group 7 in hexaploid wheat (Triticum aestivum L.), to identify gene distribution in these chromosomes, and to perform comparative studies of wheat with rice and barley. We mapped 2148 loci from 919 EST clones onto group 7 chromosomes of wheat. In the majority of cases the numbers of loci were significantly lower in the centromeric regions and tended to increase in the distal regions. The level of duplicated loci in this group was 24% with most of these loci being localized toward the distal regions. One hundred nineteen EST probes that hybridized to three fragments and mapped to the three group 7 chromosomes were designated landmark probes and were used to construct a consensus homoeologous group 7 map. An additional 49 probes that mapped to 7AS, 7DS, and the ancestral translocated segment involving 7BS also were designated landmarks. Landmark probe orders and comparative maps of wheat, rice, and barley were produced on the basis of corresponding rice BAC/PAC and genetic markers that mapped on chromosomes 6 and 8 of rice. Identification of landmark ESTs and development of consensus maps may provide a framework of conserved coding regions predating the evolution of wheat genomes.

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    • "EST-STS primer pairs that mapped physically to the distal 7AL-16 (0.86–0.90) bin [47] ( were selected to screen for polymorphisms between the IW172 and Mo75 parental lines, and the resistant and susceptible DNA pools. Out of 22 primer pairs tested, only one EST marker BE637476 was polymorphic and linked with MlIW172. "
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    ABSTRACT: Powdery mildew, caused by Blumeria graminis f. sp. tritici, is one of the most important wheat diseases in the world. In this study, a single dominant powdery mildew resistance gene MlIW172 was identified in the IW172 wild emmer accession and mapped to the distal region of chromosome arm 7AL (bin7AL-16-0.86-0.90) via molecular marker analysis. MlIW172 was closely linked with the RFLP probe Xpsr680-derived STS marker Xmag2185 and the EST markers BE405531 and BE637476. This suggested that MlIW172 might be allelic to the Pm1 locus or a new locus closely linked to Pm1. By screening genomic BAC library of durum wheat cv. Langdon and 7AL-specific BAC library of hexaploid wheat cv. Chinese Spring, and after analyzing genome scaffolds of Triticum urartu containing the marker sequences, additional markers were developed to construct a fine genetic linkage map on the MlIW172 locus region and to delineate the resistance gene within a 0.48 cM interval. Comparative genetics analyses using ESTs and RFLP probe sequences flanking the MlIW172 region against other grass species revealed a general co-linearity in this region with the orthologous genomic regions of rice chromosome 6, Brachypodium chromosome 1, and sorghum chromosome 10. However, orthologous resistance gene-like RGA sequences were only present in wheat and Brachypodium. The BAC contigs and sequence scaffolds that we have developed provide a framework for the physical mapping and map-based cloning of MlIW172.
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    • "Second, the ORF structure is conserved between rice and wheat cHsp90 genes, with three exons and two introns present in an intact ORF (Fig. 1, Table S4). Third, because of the established syntenic relationships between wheat and rice chromosomes (2 vs 4, 7 vs 8, 5 vs 9; Conley et al., 2004; Hossain et al., 2004; Linkiewicz et al., 2004), the chromosomal locations of TaHsp90.1, TaHsp90.2 and TaHsp90.3 are consistent with those of OsHsp90.1, "
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    • "Yao et al. (2007) mapped two powdery mildew resistance genes (Mlm80 and Mlm2033) on chromosome arm 7AL (interval Xmag2185–Xcfa2040) of diploid T. monococcum (genome AA) and found a distal anchor marker (Xmag1986) to BAC clone (AP006616), adjacent to the current distal anchor (XstsBE445653), on the annotated rice sequence. Quarrie et al. (2006) found high level of colinearity between wheat ESTs assigned to chromosome deletion bin 7AL-16 0.86- 0.90 and rice chromosome arm 6L, which was also in agreement with the results of Hossain et al. (2004). "
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