Analysis of intraspecific diversity of cultivated emmer <Emphasis Type="Italic">Triticum dicoccum</Emphasis> (Schrank.) schuebl using C-banding technique

Ninety-four lines of Triticum dicoccum isolated from 86 wheat accessions from Vavilov All-Russia Research Institute of Plant Industry (VIR, Russia) and INRA (Clermont-Ferrand, France) germ-plasm collections were studied using C-banding technique. Visual comparison of karyotypes of different accessions was performed to establish genetic relationships and evaluate features inherent for ecological-geographical groups. The level of C-banding polymorphism in the whole sample of tetraploid emmer proved to be relatively low. The diversity within groups was higher than the differences between them. The material studied contained 39 lines carrying 16 different types of chromosomal rearrangements including single and multiple translocations and inversions. The level of translocation polymorphism was comparable with that detected earlier for polyploid wheat species. The frequencies of individual translocation types varied from 18 (T7A:5B) to 1 (nine types). Analysis of the distribution of the most frequent translocations 7A:5B suggested that it has significant adaptive value on the territory of Europe. Similarity of the C-banding patterns of European emmer and the accessions with the same translocation of the Asian origin points to their possible common origin. The occurrence of the same translocation in several T. dicoccoides accessions from Syria and Lebanon may indicate that such forms of wild emmer could have taken part in the origin of cultivate emmer from Western Europe. Similarity of the C-banding patterns of some chromosomes of European emmer and spelt could serve as an indirect evidence of their close genetic relationships.     

Cytogenetic Analysis of Hybrids Resistant to Yellow Rust and Powdery Mildew Obtained by Crossing Common Wheat (Triticum aestivum L., AABBDD) with Wheats of the Timopheevi Group (AtAtGG)

The karyotypes of 47 hybrid lines obtained from crosses of common wheat Triticum aestivum L. (cv. Rodina and line 353) with Triticum timopheevii(Zhuk.) Zhuk. (A ^t A ^t GG) and related species T. militinae Zhuk. et Migusch. (A ^t A ^t GG) and T. kiharae Dorof. et Migusch. (A ^t A ^t GGD ^sq D ^sq) were analyzed by C-banding. Most lines were resistant to yellow rust and powdery mildew. The introgression of alien genetic material to the common wheat genome was realized via substitutions of complete A ⁺-,G-, and D-genome chromosomes, chromosome arms, or their fragments. The pattern of chromosome substitutions in resistant lines differed from that in introgressive hybrids selected for other traits. Substitutions of chromosomes 6G, 2A^t, 2G, and 5G were revealed in 31, 23, 18, and 13 lines, respectively. Substitutions of chromosomes 4G, 4A^t, and 6A^t were not observed. In 15 lines, a 5BS.5BL-5GL translocation was identified. High frequency of substitutions of chromosomes 2A^t, 2G, 5G, and 6G indicate that they may carry the resistance genes and that they are closely related to the respective homoeologous chromosomes of common wheat that determines their high compensation ability.     

Dynamics of hybrid necrosis genes in Russian cultivars of common wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.)

Study of necrosis genotypes of 72 Russian cultivars of winter common wheat has confirmed a tendency towards “washing off“ of genotypes with the Ne1 gene. Fifty-six percent of cultivars have the genotype ne1ne1Ne2Ne2, and 44% have the genotype ne1ne1ne2ne2; i.e., they are free of hybrid necrosis genes. The results of the study indicate that the diversity of the original ancestors in the groups of cultivars with the ne1ne1Ne2Ne2 and ne1ne1ne2ne2 genotypes is almost the same. This determines the instability of the tendency towards a higher prevalence of the ne1ne1Ne2Ne2 genotype in recent years. The changes in the diversity of the original ancestors with time have shown an increase in the diversity index. These processes may somewhat decrease the rate of genetic erosion caused by the fact that the Ne1Ne1ne2ne2 falls out of breeding. The routes of transmission of necrosis gene alleles from ancestors to descendants have been traced using extended pedigrees, and this information has been used to identify the probable donors and sources of hybrid necrosis gene alleles. In most cases, the cultivars Mironovskaya 808 and Krasnodarskaya 39 are the putative sources of the Ne2 allele (60.6 and 27.3% of all cases, respectively). The old cultivar Gostianum 237 from Saratov oblast is the putative source of the Ne2 allele in the cultivar Krasnodarskaya 39. The cultivars Bezostaya 1 and Odesskaya 51 (whose pedigree also includes Bezostaya 1) are the donors of the recessive genotype ne1ne1ne2ne2 in 93.5% of cases. The old Ukrainian cultivar Ukrainka is the most frequent source of recessive alleles. The strength of the Ne2 allele has been estimated in 36 cultivars. The results indicate that modifier genes affect the expression of tumor necrosis genes.     

New data on the distribution of hybrid necrosis genes in winter bread wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.) cultivars

Hybrid necrosis genotypes have been identified in 125 Russian cultivars of winter bread wheat. More than half of them (56%) carry the Ne2 gene (genotype ne1ne1Ne2Ne2); others are free of necrosis genes (genotype ne1ne1ne2ne2). The possible causes of the increase in the Ne2 allele frequency and the loss of the Ne1Ne1ne2ne2 genotype in modern Russian cultivars of winter wheat are discussed. The principal component method has been used to compare the structures of the genetic diversity of cultivars differing in the hybrid necrosis genotype. It has been found that the Ne2 allele in winter wheat cultivars from northern Russia has originated from the cultivar Mironovskaya 808, whereas the cultivar Bezostaya 1 is not a source of this gene. In cultivars from southern Russia, the presence of the Ne2 allele is also mainly accounted for by the use of Mironovskaya 808 wheat in their breeding. The recessive genotype is explained by the presence of descendants of the cultivar Odesskaya 16 in the pedigrees of southern Russian winter wheats. The genetic relationship of cultivars with identical and different necrosis genotypes has been analyzed in nine regions of the Russian Federation.     

Distribution of Hybrid Necrosis Alleles in Genotypes of Aboriginal Common Wheat Cultivars from Afghanistan,Palestine, and Transjordan

Russian Journal of Genetics - Necrotic genotypes of the aboriginal common wheat cultivars (Triticum aestivum L.) from Iran, Afghanistan, Palestine, and Transjordan were studied. It was shown that...     

Intergenomic chromosome substitutions in wheat interspecific hybrids and their use in the development of a genetic nomenclature of <Emphasis Type="Italic">Triticum timopheevii</Emphasis> chromosomes

The results of analysis of the genome formation in interspecific hybrids of Triticum aestivum with T. timopheevii are reviewed. The spectra of substitutions and rearrangements are shown to depend on the genotypes of the parental forms and on the direction of selection. The frequencies of substitutions of individual T. timopheevii chromosomes significantly vary and reflect the level of their divergence relative to the common wheat chromosomes. Some aspects of classification of the A^t- and G-genome chromosomes are discussed.