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Materials and methods

Thirty families, consisting of one hundred thirty-six plants, were derived from two independent crosses of Triticum aestivum L. em Thell. cvs. Wichita (WI) and Newton (NWT) with T. araraticum (Fig. 1). The used accession of T. araraticum., TA 39 from Iraq, is maintained at the Wheat Genetics Resource Center, Kansas State University, Manhattan, Kansas, USA. From two to 13 plants were analyzed in each family. A modified C-banding technique was used for karyotype analysis (Badaeva et al. 1994). Chromosomes of common wheat, T. aestivum, and T. araraticum were classified according to genetic nomenclature (Gill et al. 1991; Badaeva et al. 1991).


Results and discussion

Cytogenetic analysis of hybrid lines showed that the majority of plants had a chromosome number of 2n=42 (Fig. 2a). Two plants were exceptional. Plant #4 of KS88-9-8 with 2n=43 had a 5G(5B) 6G(6B) double disomic substitution and 4G monosomic addition. Plant #3 of KS88-14-3 with 2n=41 was monosomic for 1 G(1B) and had a double disomic 5A^t(5A) 6G(6B) substitution.

Twenty-six plants from eight families shared the common chromosome rec 7AS-7A^tL. Two plants of KS88-16-2 had one 6B and one 6G chromosome. Telocentric 5BL chromosome in homozygous or heterozygous state was discovered in 11 plants of six families. Twenty-eight plants belonging to nine families had a terminal deletion of 1 BL (Fig. 2b). The modified 1 B chromosome was present in homozygous condition in all plants of KS88-17-1 and KS88-17-6, and was found in homozygous or heterozygous condition in a few plants of the other families. The number of substitutions per karyotype ranged from 0 to 3, and nine different substitution types were recovered (Table 1).

The first type was found only in the KS88-2-2 family, where six plants were homozygous and one plant was heterozygous for rec 7AS-7A^tL chromosome. This chromosome had telomeric and subtelomeric bands in the short and a faint proximal band near the centromere in the long arm which were typical of normal chromosome 7A. A large intercalary C-band in the distal half of the 7At long arm indicates that the cross-over site was probably located in the proximal part of the long arms of 7A and 7A^t. Two types of single disomic substitutions were found. Single 2G(2B) disomic substitutions were identified in five families. In four of these families the rec 7A-7A^t chromosome was also present. Single disomic 6G(6B) substitution was found in six families. In KS88-16-2, one plant was heterozygous for the rec 7A-7At chromosome.

There were two types of double disomic substitution. Double disomic substitution 3At(3A) 6G(6B) was found in all plants of KS88-7-2 family. One plant of KS88-14-3 and one plant of KS88-17-6 had a I G(I D) 6G(6B) double disomic substitution.

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