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Theoretical and Applied Genetics

, Volume 98, Issue 3–4, pp 365–370 | Cite as

FISH to meiotic pachytene chromosomes of tomato locates the root-knot nematode resistance gene Mi-1 and the acid phosphatase gene Aps-1 near the junction of euchromatin and pericentromeric heterochromatin of chromosome arms 6S and 6L, respectively

  • X.-B. Zhong
  • J. Bodeau
  • P. F. Fransz
  • V. M. Williamson
  • A. van Kammen
  • J. H. de Jong
  • P. Zabel

Abstract

 The root-knot nematode resistance gene Mi-1 in tomato has long been thought to be located in the pericentromeric heterochromatin region of the long arm of chromosome 6 because of its very tight genetic linkage (approx. 1 cM) to the markers Aps-1 (Acid phosphatase 1) and yv (yellow virescent). Using Mi-BAC clones and an Aps-1 YAC clone in fluorescence in situ hybridisation (FISH) to pachytene chromosomes we now provide direct physical evidence showing that Mi-1 is located at the border of the euchromatin and heterochromatin regions in the short arm (6S) and Aps-1 in the pericentromeric heterochromatin of the long arm (6L) close to the euchromatin. Taking into account both the estimated DNA content of hetero- and euchromatin regions and the compactness of the tomato chromosomes at pachytene (2 Mb/μm), our data suggest that Mi-1 and Aps-1 are at least 40 Mb apart, a base pair-to-centiMorgan relationship that is more than 50-fold higher than the average value of 750 kb/cM of the tomato genome. An integrated cytogenetic-molecular map of chromosome 6 is presented that provides a framework for physical mapping.

Key words Fluorescence in situ hybridisation FISH Pachytene chromosomes Nematode resistance gene Mi Tomato 

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Copyright information

© Springer-Verlag Berlin Heidelberg 1999

Authors and Affiliations

  • X.-B. Zhong
    • 1
  • J. Bodeau
    • 2
  • P. F. Fransz
    • 1
  • V. M. Williamson
    • 2
  • A. van Kammen
    • 1
  • J. H. de Jong
    • 1
  • P. Zabel
    • 1
  1. 1.Department of Biomolecular Sciences, Wageningen Agricultural University, Dreijenlaan 3, 6703 HA Wageningen, The Netherlands Fax: +31 317 483584 E-mail: office@alg.mb.wau.nlNL
  2. 2.CEPRAP, University of California, Davis CA 95616, USAUS

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