The Genetic Structure Features of the Pinus sylvestris L. Population in the Steppe Zone of European Russia

The article presents the results of studу of the genetic structure of Scots pine (Pinus sylvestris L.) growing in the ecologically favorable territory of the steppe zone of European Russia. 35–year-old pine forest plantations (the Voronezh Region, Kantemirovskiy District, the 3rd bonitet class, forest site type – A1, a random sample, 60 trees) have been chosen as the object of the study. Genetic diversity has been examined on the basis of the microsatellite analysis of 18 SSR-loci (14 EST-SSR-loci and 4 nSSR-loci) and two isozymic loci (shikimate dehydrogenase and glutamate dehydrogenase – or Skdh and Gdh, respectively). It has been revealed that in the studied population, all the used microsatellite loci, with the exception of lw_isotig02842, are polymorphic. The average values of genetic variability calculated from the microsatellite loci have been obtained: the proportion of the polymorphic loci – 94.44 %, the average number of alleles per locus – 3.500, the average effective number of alleles – 2.466, the observed and expected heterozygosity – 0.209 and 0.493 respectively; the Wright fixation index – 0.577. In terms of the level of allelic diversity, the plantation is characterized by relatively lower values of genetic and statistical population parameters (the average observed and expected heterozygosity) compared to the natural forest-steppe populations of the Central Chernozem Region. A high positive Wright fixation index indicates the presence of an increased proportion of inbreeding in the steppe population trees. The reasons and possible nature of the revealed phenomenon are discussed. Based on the isoenzyme analysis, the genetic structure of the Skdh and Gdh loci is examined. The results of the analysis indicate a high frequency of the rapid allele Skdh-11 (82 %) and the embryonic semi-lethal allele Gdh-11 (22 %), which, apparently, can be considered as one of the mechanisms of the population adaptation to the conditions of a warmer and drier climate of the steppe region. A deficiency of glutamate dehydrogenase heterozygotes has been established. It has also been noted that the groups of EST-SSR-loci and nSSR-loci differ in the level of genetic variability and population structure. It has been shown that the combined use of different types of genetic markers makes it possible to obtain more complete and objective information on the distinctive features of the genetic structure of pine forests in the optimal and pessimal zones of the range. The studied 18 microsatellite loci can be used to assess the genetic diversity of Scots pine populations and trees in the steppe region of European Russia.