ISSN 1022-7954, Russian Journal of Genetics, 2009, Vol. 45, No. 11, pp. 1376–1384. © Pleiades Publishing, Inc., 2009. Original Russian Text © S.A. Zoshchuk, N.V. Zoshchuk, A.V. Amosova, O.S. Dedkova, E.D. Badaeva, 2009, published in Genetika, 2009, Vol. 45, No. 11, pp. 1556–1564. 1376 INTRODUCTION Cereals are characterized by high DNA content, repetitive DNA sequences (RS) accounting for a major portion (75–95%) of total DNA [1–4]. Tandemly repeated DNA sequences, the proportion of which in the genomes of some species can reach 10 to 20% [5], are of particular interest. Tandem repeats mostly local- ize in heterochromatin regions [5–9] of functionally important chromosome segments such as telomeres and centromeres [10–14]. In many cases, tandem repeats are responsible for substantial differences in DNA con- tent between closely related species. The present day polyploid wheats are represented by two evolutionary groups, Emmer and Timopheevi. Wheat species belonging to these groups are character- ized by different genomic composition. They are also different in a number of morphological, biochemical, molecular, and cytological characters [15–18]. It is sug- gested, that Emmer and Timopheevi groups were formed independently as a result of hybridization of the same parental forms, T. urartu and Ae. speltoides [19, 20]. However, divergence of Emmer wheats occurred much earlier than of the Timopheevi group [21, 22]. Reorganization of repetitive DNA sequences is thought to play an important role in speciation [23, 24]. New tandem repeat families arise as a result of sequence divergence, associated with the change of the repeat composition, accompanied by their amplifica- tion, elimination, or re-distribution in the genome [25-27]. Some repeat families are typical of large tax- onomic groups, other families are typical of individual species and even chromosomes [24, 28–31]. The Spelt-1 family examined in the present study is present in the genomes of Ae. speltoides and polyploid wheats and belongs to the group of genome-specific repeats [32]. The present study was focused on the analysis of intra- and interspecific diversity in the distribution of the Spelt-1 repeats among the chromosomes of tetrap- loid and hexaploid wheat species representing Emmer evolutionary lineage, T. dicoccoides, T. dicoccum, T. durum, T. polonicum, T. carthlicum, T. aethiopicum, and T. aestivum by means of fluorescent in situ hybrid- ization. To evaluate the dynamics of Spelt-1 sequence changes during wheat evolution, our results were com- pared with those for the wheats of Timopheevi group obtained earlier [33], as well as with the data for Ae. speltoides, the putative donor of B genome [34]. Intraspecific Divergence in Wheats of the Emmer Group Using In Situ Hybridization with the Spelt-1 Family of Tandem Repeats S. A. Zoshchuk a , N. V. Zoshchuk a , A. V. Amosova a , O. S. Dedkova b , and E. D. Badaeva a a Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Moscow, 119991 Russia; e-mail: k_badaeva@mail.ru b Vavilov Institute of General Genetics, Russian Academy of Sciences, Moscow, 119991 Russia Received May 5, 2009 Abstract—Fluorescence in situ hybridization (FISH) was used to study the distribution of Spelt-1 repetitive DNA sequences on chromosomes of 37 accessions representing eight polyploidy wheat species of the Emmer evolutionary lineage: Triticum dicoccoides Körn, T. dicoccum (Schrank) Schuebel, T. durum Desf., T. poloni- cum L., T. carthlicum Nevski, T. aethiopicum Jakubz., T. aestivum L., and T. spelta L. Substantial polymor- phism in the number, distribution, and the sizes of the Spelt-1 loci was revealed. On the chromosomes of the accessions examined, Spelt-1 tandem repeats were found in seven different positions (per haploid chromosome set). These were “potential hybridization sites”, including the subtelomeric regions of either short or long arms of chromosomes 2A and 6B, the short arm of chromosome 1B, and the long arms of chromosomes 2B and 3B. However, in individual genotypes, only from one to three Spelt-1 loci were revealed. Furthermore, no hybrid- ization with Spelt-1 probe was detected on chromosomes from 12 accessions. Thus, the total number of Spelt-1 sites in karyotypes varied from zero to three, with the average number of 1.16. This was substantially lower than in the species of the Timopheevi section and diploid Aegilops speltoides Tausch, a putative donor of the B genome. The decrease of the content of Spelt-1 sequences in the genomes of the Emmer group wheats in com- parison with the species of the Timopheevii group and diploid Ae. speltoides was assumed to result from the repetitive sequences reorganization during polyploidization and the repeat elimination during wheat evolution. DOI: 10.1134/S102279540911012X EXPERIMENTAL ARTICLES