[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.

[Genetic differentiation of common wheat cultivars using multiple alleles of gliadin-coding loci].

The alleles ofgliadin-coding loci have been identified in 105 spring common wheat cultivars bred in Omsk and Saratov by polyacrylamide gel electrophoresis. It has been shown that 49% of the Omsk cultivars and 40% of the Saratov cultivars are heterogeneous, i.e., composed of several biotypes that differ in alleles of the gliadin-coding loci. A total of 278 genotypes have been determined (170 in the Saratov cultivars and 112 in the Omsk cultivars); in these two groups of cultivars, four genotypes are identical. Due to this heterogeneity, the cultivars bred in Omsk and Saratov can be differentiated in a statistically significant manner despite their close kinship, which allows them to be ascribed an accession to a particular breeding center based on the gliadin pattern and the number or frequency of biotypes, as well as to determine its species affiliation with a 95% probability. Close relations prevent 5% of the Saratov cultivars and 4.4% of the Omsk cultivars from being distinguished within populations, since they have identical alleles of gliadin-coding loci.

[Comparative analysis of the genetic diversity dynamics at gliadin loci in the winter common wheat Triticum aestivum L. cultivars developed in Serbia and Italy over 40 years of scientific breeding].

The dynamics of genetic transformations at gliadin-coding loci in the winter common wheat cultivars produced in Serbia and Italy over 40 years of scientific breeding was studied. It was demonstrated that a number of alleles unique for the wheat cultivars of each country were substituted with the alleles of a limited number of donor cultivars, in particular, cultivar Bezostaya 1 and its derivatives. On the background of preserved heterogeneity values during various time periods of breeding in each country, the genetic diversity in the total region decreased, as demonstrated by similarity in the sets of alleles of gliadin loci and their frequencies in the modem cultivars of these two Southern European countries. This decrease in the genetic diversity is an erosion of genetic resources within the region, which results in a loss of unique coadapted gene complexes.

[A comparison of two existing catalogues 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 catalogue 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.

C, N, and noble gas isotopes in grain size separates of presolar diamonds from Efremovka.

Nanometer-size presolar diamonds from the Efremovka CV3 chondrite were physically separated into several grain size fractions by ultracentrifugation. The coarsest size fraction is the most enriched in carbon-12; the others have broadly similar carbon isotopic compositions. Measurement of noble gases shows that their concentration decreases with decreasing grain size. This effect is attributed to ion implantation. Such an episode could occur in the envelope of a supernova that produced the diamonds, or in interstellar space; in either case, ions with energies above a certain threshold pass completely through the smaller diamond grains without being captured. Concentrations of nitrogen show only minor variations with grain size, indicating a different mechanism of incorporation into the diamonds.