Based on a C-banded chromosome analysis of Triticum aestivum x T. timopheevii hybrid lines, we developed a classification of the A(t) and G genome chromosomes that agrees with the standard genetic nomenclature of T. aestivum chromosomes. Transfer of genetic material from T. timopheevii to T. aestivum involved complete chromosomes, chromosome arms, or segments. Frequencies of chromosome substitution were highest for homoeologous group 2 and lowest for group 4. Moreover, B(G) substitutions were frequent compared to A(A(t)). The pattern of chromosome substitutions and rearrangements were unequal and depended on the genotype of the parental T. aestivum cultivar.

The tetraploid wheat Triticum timopheevii Zhuk (AtAtGG) is known as a source of genes determining resistance to many diseases. An introgressive line 842, with durable resistance to leaf rust was established by crossing T. aestivum cv. ‘Saratovskaya29’ with T. timopheevii ssp. viticulosum and used for mapping leaf rust resistance genes. Molecular analysis of the line 842 with polymorphic microsatellite markers detected introgressions of T. timopheevii into the homoeologous group 2 chromosomes of common wheat. Transloca‐tion breakpoints of introgressed fragments were localized between the markers Xgwm95 and Xgwm817 on chromosome 2A, as well as Xgwm1128 and Xgwm1067 on chromosome 2B. Linkage analysis demonstrated the association of disease resistance at the seedling stage with chromosome 2A. The gene was found to be linked with marker Xgwm817 at a genetic distance of 1.5 cM. The alien leaf rust resistance gene was temporarily designated as lrTt1.

A collection of introgression lines was obtained from crosses of common wheat (Triticum aestivum L.) cultivars with tetraploid wheat Triticum timopheevii (Zhuk.). Evaluation of resistance to fungal diseases revealed the lines with resistance to leaf and stem rusts, powdery mildew, spot blotch, and loose smut, the most widespread in Siberian region of Russia. Localization of the T. timopheevii genome fragments by means of microsatellite markers determined higher frequency of substitutions and translocations on chromosomes 1А, 2A, 2B, 5A, 5B and 6B. Molecular mapping of the loci determining leaf rust resistance revealed two independent loci on chromosomes 5B and 2A. The major locus on 5BS.5BL-5GL translocated chromosome accounting 64% of the phenotypic variance of the trait was found to be closely linked to microsatellite markers Xgwm814 and Xgwm1257. The other, minor locus, controlling 11% of the trait was mapped next to Xgwm312 on chromosome 2A. Microsatellite markers located near these genes may be used for controlling the transfer of valuable traits in new wheat cultivars.

No abstract

No abstract