[Phylogenetic Analysis of Ukrainian Isolate of Beet Necrotic Yellow Vein Virus].

The analysis of Ukrainian isolate of beet necrotic yellow vein virus has been performed. The partial nucleotide sequence of cDNA corresponding to RNA-2 of BNYVV isolates were analyzed and Ukrainian isolate AG9 of BNYVV was assigned to type A strains based on DNA sequences. The nucleotide sequence of gene encoding a coat protein of Ukrainian isolate of BNYVV was compared with appropriate nucleotide sequences existing in the GeneBank and the phylogenetic analysis of investigated virus was done. It was shown that Ukrainian isolate AG9 of BNYVV has 100 % homology to isolate originating from Sweden.

[Spontaneous nucleotide substitution in potato virus X genes].

Elucidation of the factors underlying nucleotide substitution types and rates in genomes is of significance for improving the prevalent models for molecular evolution, and is essential in studying the evolution process, distinguishing the coding and noncoding RNAs, identifying biologically significant motifs such as replication signals, control regions and so on. However, many questions concerning the factors that affect the nucleotide substitutions in plant virus genomes still remain unclear. In this paper a comparative computer analysis of nucleotide substitution in genomic sequences of 10 pairs of closely related potato virus X (PVX) strains having equal genome and gene length has been carried out. A significant frequency variation of nucleotide substitutions, depending on nucleotide and strain pairs, length and localization of genome and gene regions as well as substitution types and their codon positions, was found. The highest relations of substitution frequency are found in different nucleotide pairs (u-->c/c-->g, 1240), codon positions (third/second, 17.3) and substitution types (transitions/transversions, 5.8), the least ones - in forward and back substitutions in the same nucleotide pairs (1.03-1.6). The transversion frequencies are generally significantly lower but more variable than the transition one, and there is no direct relationship between gene (region) length and transversion frequency.