, Volume 97, Issue 8, pp 1380-1386

Elimination of a tandem repeat of telomeric heterochromatin during the evolution of wheat

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Abstract

 An analysis of accessions of Triticum and Aegilops species (86 diploid, 91 tetraploid and 109 hexaploid) was performed using squash-dot hybridization with the tandem repeat Spelt1 sequence as a probe. The Spelt1 sequence is a highly species-specific repeat associated with the telomeric heterochromatin of Aegilops speltoides Boiss. in which its copy numbers vary from 1.5×105 to 5.3×105. The amounts of Spelt1 are sharply decreased in tetraploid and hexaploid species and vary widely from less than 102 to 1.2×104. Two tetraploid wheats, Triticum timopheevii Zhuk. and T. carthlicum Nevski, are exceptional endemic species and within their restricted geographical distributions maintain the amounts of Spelt1 unaltered. The Spelt1 repetitive sequence was localized on the 6BL chromosome of tetraploid wheat Triticum durum Desf. cv ‘Langdon’ by dot-hybridization using D-genome disomic substitution lines. The possible causes of the loss of the telomere-associated tandem repeat Spelt1 in the process of wheat evolution and polyploidization are discussed.

Received: 5 March 1998 / Accepted: 28 May 1998