LTR-retrotransposons of the family Pseudoviridae in the genomes of monocotyledonous and dicotyledonous plants. Elkina M.A., Glazko V.I. Russian State Agrarian University - Moscow Timiryazev Agricultural Academy mariya elkina@ya hoo.com LTR-retrotransposons occupy a significant part of the genome of plant (just over 7% of the genome of Arabidopsis thaliana, 25% - of the rice genome, 65% - of the genome of wheat, 75% - of the ma ize genome. Due to their mobility these elements can cause a variety of mutations and recombinations as well as deletions and translocations as a result of transposition. Taking into account the fact that the induction of transpositions incr eased under the conditions of environmental changes, transposable elements are an important tool of evolution [1]. We tried to estimate the distribution of inverted sites of LTR-retrotransposons of the fa mily Pseudoviridae in the genomes of crop plants using multi-locus genotyping and the possibility of polymorphism obtained by PCR with primers homolo gous to fragments of these retrotransposons to study the genetic structure of populations of monocots and dicots reproducing in differ ent environmental conditions. Were chosen repr esentatives of the class of monocots (Triticum aestivum L.), and dicots (Glycine soja Sieb. Et Zucc and Glycine max Merrill) to analyze the possibility of using sites of LTR retrotransposons as molecular markers in genetic studies of population's structure of plants . Three varieties of wheat wer e studied: two varieties of winter wheat Moscow 39 (soft winter) - and Mironovskaya 808 (soft winter, derived from the spring) - and a variety of spring wheat Omsk 36 (soft spring), and 5 populations of wild soybean species Glycine soja Sieb. et Zucc (Primorsky Region) and representatives of Polukulturnaya C 10 (Glycine max Merrill, China). The studies of the genetic structure of populations wer e carried out on the base of polimor fism of DNA's fragments as results of IRAP-PCR (Inter-Retrotransposon Amplyfied Polymorphism), flanked by inverted s ites of LTR-retrotransposon soybean's LTR-retrotransposon LTR SIRE-1 (GCA-GTT-ATG-CAA-GTG-GGA-TCAGCA), belonging to the fa mily Pseudoviridae, genus Sireviruses. We obtained a spectra of clearly r eplicating DNA fragments as a result of IRAP-PCR with a primer to a ter mina l site of r etroelement LTRSIRE-1 as in soybea n (Glycine soja Sieb. et Zucc and Glycine max Merrill), and in wheat (Triticum aestivum L.). The fragments were of the sa me length (15 loci 350-1010 bp, 26 bp 220-1450 loci respectively. Only one monomorphic locus (700 bp) was detected in soybea n (Glycine soja Sieb. et Zucc and Glycine max Merrill), the share of polymorphic loci (P) on the primer was 93%, PIC