Genetic classification of Aegilops columnaris Zhuk. (2n=4x=28, UcUcXcXc) chromosomes based on FISH analysis and substitution patterns in common wheat × Ae. columnaris introgressive lines.

Aegilops columnaris is a tetraploid species originated from Ae. umbellulata (2n=2x=14, UU) and a yet unknown diploid grass species. Although Ae. columnaris possesses some agronomically valuable traits, such as heat and drought tolerance and resistance to pests, it has never been used in wheat breeding because of difficulties in producing hybrids and a lack of information on the relationships between Ae. columnaris and common wheat chromosomes. In this paper, we report the development of 57 wheat - Ae. columnaris introgressive lines covering 8 of the14 chromosomes of Aegilops. Based on substitution spectra of hybrids and the results of FISH analysis of the parental Ae. columnaris line with seven DNA probes, we have developed the genetic nomenclature of the Uc and Xc chromosomes. Genetic groups and genome affinities were established for 11 of 14 chromosomes; the classification of the remaining three chromosomes remains unsolved. Each Ae. columnaris chromosome was characterized on the basis of C-banding pattern and the distribution of seven DNA sequences. Introgression processes were shown to depend on the parental wheat genotype and the level of divergence of homoeologous chromosomes. We found that lines carrying chromosome 5Xc are resistant to leaf rust; therefore, this chromosome could possess novel resistance genes that have never been utilized in wheat breeding.

[Genetics and Genomics of Wheat: Storage Proteins, Ecological Plasticity, and Immunity].

Recent advances in genetics and genetic research methods made it possible to explain the large polymorphism observed among storage proteins of wheat weevil (gliadins and glutenins), to determine their genetic control mechanism, and to develop a system for the identification of wheat genotypes on the basis of multiple allelism. This system has extremely high sensitivity and efficiency, which makes it possible to conduct studies to determine the purity and authenticity of wheat varieties, the dynamics of alleles diversity in time and space, the phylogenetics, etc., through the use of an extensive database on the allelic composition of gliadin loci. An investigation of the molecular structure of genes controlling the synthesis of storage proteins and their organization on chromosomes, as well as an analysis of wheat genome structure, revealed the molecular mechanisms of variability in the wheat genome and its reorganization in response to changes in environmental conditions and cultivation technologies. The multilevel genetic system of protection against pathogens and adverse environmental factors that developed in the course of wheat evolution continues to astound researchers' imagination with new resistance genes and novel types of antimicrobial peptides having been discovered and sequenced in recent years and the diversity of their structures and mechanisms of action in response to pathogens. An analysis of gene sequences involved in wheat domestication, namely, those that define ecological plasticity, i. e. the type of plant development (Vrn genes), and those responsible for spikelet traits (Q genes), which ensured the successful cultivation of wheat by humans, revealed that the basis for these features are specific mutations.

[Genetic diversity of common wheat varieties at the gliadin-coding loci].

One hundred and fifty Russian and foreign winter common wheat varieties were examined by the PAGE method. A total of 70 alleles were identified at seven gliadin-coding loci. It was demonstrated that 42% of varieties were heterogeneous, i.e., were represented by a number of genotypes, while 52% of varieties were homogeneous. A unique combination of gliadin alleles was typical of 91.3% of examined varieties, while 8.7% of varieties had identical alleles of all gliadin-coding loci and were indistinguishable. Frequent and rare alleles were identified, with the former accounting for 18.6% of all alleles. It was demonstrated that allelic diversity at the Gli-2 loci (47 alleles) was almost twice that at the Gli-1 loci (23 loci) and was determined by the number of rare alleles. New alleles for the winter common wheat, including three alleles of the GliA2 locus and two alleles of the Gli-B2 locus, were determined. A tendency toward a reduction of the genetic diversity level in modern varieties, which was due to the use of identical parental varieties in breeding programs, was identified.