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.     

Dynamics of genetic diversity in winter common wheat Triticum aestivum L. cultivars released in Russia from 1929 to 2005

Genealogical analysis was used to study the dynamics of genetic diversity in Russian cultivars of winter common wheat from 1929 to 2005. The Shannon diversity index of the total set of released cultivars remained almost unchanged, although the number of original ancestors (landraces and genetic lines) increased almost tenfold in the period under study. This was explained in terms of the dependence of the modified Shannon diversity index on two parameters, the number of original ancestors and the mean coefficient of parentage. Significant direct effects were revealed: a positive effect of the former parameter and a negative of the latter. As a result, the increase in the number of original ancestors was compensated by the increase in relatedness of cultivars. Genetic erosion of released diversity was observed, as a half of Russian landraces were lost. Although the mean coefficient of parentage did not reach its critical value $(\bar R = 0.25)$ , cultivars of some regions (Central and Volga-Vyatka) proved to be closely related. A favorable gradual decrease in the mean coefficient of parentage was observed in the past 15 years. A set of modern winter wheat cultivars, which were introduced in the Russian Official List from 2002 to 2005, displayed a cluster structure. The overwhelming majority of cultivars formed two clusters originating from Bezostaya 1 (67% of cultivars) and Mironovskaya 808 (31%).     

A comparison of two existing catalogs of the alleles of gliadin-coding loci in winter common wheat

Two catalogs of alleles of gliadin-coding loci, controlling synthesis of a storage protein of wheat caryopsis, gliadin, were compared. One catalog comprises the alleles detected according to the electrophoretic patterns in starch gels; the other, in polyacrylamide gels. Determination of the allelic state of gliadin-coding loci in 31 previously not studied cultivars of winter common wheat allowed us to construct a matching system for the alleles compiled in the two catalogs, which gives the possibility to compare the results of wheat cultivar analyses performed at different scientific institutions.     

Analysis of Genetic Diversity of Spring Durum Wheat (<Emphasis Type="Italic">Triticum durum</Emphasis> Desf.) Cultivars Released in Russia in 1929–2004

Based on genealogical analysis, the genetic diversity of 78 spring durum wheat cultivars released in Russia in 1929–2004 have been examined. The temporal trends of change in diversity were studied using series of n × m matrices (where n is the number of the cultivars and m is the number of original ancestors) and calculating coefficients of parentage in sets of cultivars released in particular years. The pool of original ancestors of spring durum wheat cultivars includes 90 landraces and old varieties, more than a half (57%) of which originate from European countries, including Russia and Ukraine (45%). The original ancestors strongly differ in the frequency of presence in the cultivar pedigrees. Landraces Beloturka, Sivouska, Kubanka (T. durum Desf.), Transbaikalian emmer, Yaroslav emmer (T. dicoccum Schuebl.), Poltavka (T. aestivum L.), and the original ancestors of cultivars Kharkov 46, Narodnaya, and Melanopus 1932 enter in the pedigrees of more than half of cultivars created within the framework of various breeding programs. At that, their distribution by cultivars from different breeding centers strongly varies. Analysis of temporal dynamics of genetic diversity, based on genetic profiles and coefficients of parentage, has shown that the genetic diversity of Russian durum wheats increased during the period examined. Nevertheless, genetic erosion of the local material—a loss of approximately 20% of the pool of Russian original ancestors—has been found. The contribution of the original ancestors to the pedigrees of different cultivars, constructed in different breeding centers and recommended for cultivation in different regions, has been estimated. The variation of the released cultivars was highest in the Lower Volga region and lowest in the Ural region. In all, the lower threshold of genetic diversity in all regions does not reach the critical level, corresponding to the similarity of half-sibs. The set of modern cultivars included in the Russian Official List 2004 has a cluster structure.     

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.     

Dynamics of Genetic Variation at Gliadin-Coding Loci in Saratov Cultivars of Common Wheat Triticum aestivum L. over Eight Decades of Scientific Breeding

Based on analysis of gliadin patterns in common wheat cultivars bred at the Research Institute of Agriculture of the Southeast, allele composition dynamics in gliadin loci has been surveyed for the period of over eight decades. It was shown that long-term breeding of the wheat cultivars involved gradual replacement of alleles characteristic of ancient cultivars for those widely spread in the world, which are probably linked with alleles that currently confer advantage to their carriers. The process of reduction of interpopulation genetic diversity in wheat (with special reference to the allele frequency dynamics at gliadin loci) is discussed. This process is responsible for genetic erosion of the species.     

Relevance of RAPD Analysis for Revealing Phylogenetic Relationships between Cultivars of Durum Wheat Triticum durum Desf.

A comparison of similarity indices between 64 durum wheat cultivars calculated using pedigree analysis and RAPD method showed a correspondence between these two approaches to estimation of genetic diversity. The associations between the results of RAPD clustering and coefficients of parentage (² test) and the coefficient of correlation between similarity matrices were statistically significant. However, the correlation was rather weak while pedigree analysis and RAPD method did not yield completely identical estimates of genetic diversity in the set of cultivars studied.     

Chromosomal Passports Provide New Insights into Diffusion of Emmer Wheat

Emmer wheat, Triticum dicoccon schrank (syn. T. dicoccum (schrank) schÜbl.), is one of the earliest domesticated crops, harboring a wide range of genetic diversity and agronomically valuable traits. The crop, however, is currently largely neglected. We provide a wealth of karyotypic information from a comprehensive collection of emmer wheat and related taxa. In addition to C-banding polymorphisms, we identified 43 variants of chromosomal rearrangements in T. dicoccon; among them 26 (60.4%) were novel. The T7A:5B translocation was most abundant in Western Europe and the Mediterranean. The plant genetic resources investigated here might become important in the future for wheat improvement. Based on cluster analysis four major karyotypic groups were discriminated within the T. dicoccon genepool, each harboring characteristic C-banding patterns and translocation spectra: the balkan, asian, european and ethiopian groups. We postulate four major diffusion routes of the crop and discuss their migration out of the Fertile Crescent considering latest archaeobotanical findings.