Resolving the aphid resistance locus Sd-1 on a BAC contig within a sub-telomeric region of Malus linkage group 7

Volkan Cevik, Graham J King

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25 Citations (SciVal)


Aphids cause serious physical and economic damage to most major crops throughout the world, and there is a pressing requirement to isolate genes conferring aphid resistance. The Sd-1 locus in Malus spp. (apple) confers resistance against the rosy leaf-curling aphid (Dysaphis devecta Wlk.), and was recently positioned within a 1.3-cM region on linkage group 7, flanked by molecular markers. These markers were used as a basis for development of a BAC contig spanning the locus, together with adapter-mediated amplification of flanking sequences to obtain BAC insert-end sequences, and fingerprinting of BAC clones. Approximately 800 kb of the Sd-1 genomic region was covered by 19 overlapping BACs, with an average insert size of 75-150 kb. The physical-genetic distance ratio was estimated at 460 kb/cM, although the distribution of recombination events was irregular with respect to estimated physical distance. Recombinant analysis and development of new markers allowed Sd-1 to be positioned within an interval of approximately 180 kb located on either of two overlapping BACs. From one of these, an insert end sequence showed a significant degree of similarity to nucleotide binding site-leucine rich repeat (NBS-LRR) resistance genes. Fluorescent in situ hybridization (FISH) of BAC clones within the contig enabled positioning and orientation of the locus within a euchromatic region, very close to the telomere of linkage group 7.

Original languageEnglish
Pages (from-to)939-945
Number of pages7
JournalGenome Biology
Issue number5
Publication statusPublished - Oct 2002


  • Animals
  • Aphids
  • Base Sequence
  • Chromosome Mapping
  • Chromosomes, Artificial, Bacterial
  • Chromosomes, Plant
  • DNA Primers
  • Genes, Plant
  • Genetic Linkage
  • Genetic Markers
  • In Situ Hybridization, Fluorescence
  • Malus
  • Plant Diseases
  • Telomere
  • Journal Article
  • Research Support, Non-U.S. Gov't


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