Molecular study of turnip mosaic virus population in the Czech Republic

Turnip mosaic virus (TuMV) is the most important virus of brassica crops. In our study, we compare the genetic structure of two Czech TuMV populations sampled in the country's 25-year interval of virus presence. The 21 isolates, mainly infecting rutabaga and horseradish, were collected from four farms under organic production, and nearly complete genome sequences, 9 596-9 787 nt in length, were obtained using Sanger sequencing for all of them. The analysis of variability and polymorphism showed differences in genetic structure but the relative stability of both populations and moderate negative selection as a factor affecting the current TuMV population. The newly collected isolates are characterised by a relatively high frequency of intralineage recombinants; interlineage recombinants were not detected compared to the 25-year-old population. The phylogenetic analysis allowed the classification of all Czech isolates into world-B phylogroup, with the prevalence of isolates of subgroup B2. The spread of isolates belonging to the other phylogenetic groups posing higher phytopathological risk, which were present in the old population and some surrounding countries, was not found.