Tomato black ring virus (TBRV), a member of the Nepovirus genus, is a serious plant pathogen distributed worldwide. It causes significant damage to several economically important crops, such as artichoke or strawberry. The TBRV bipartite genome consists of two polyadenylated single‐stranded positive‐sense RNA molecules, which may be accompanied by subviral particles such as defective interfering RNAs (DI RNAs) and satellite RNAs (satRNAs). In this study, we obtained the complete genome sequence of six TBRV isolates originating from different hosts and determined the presence of eight TBRV satRNAs. Subsequently, genetic variability, recombination, phylogenetic and selection pressure analyses were performed. The results revealed that the TBRV population is genetically diverse. The occurrence of potential recombination events, evidence of positive selection pressure acting on particular codons and the diversification of satRNAs within the TBRV population indicated that the virus mutates and can rapidly adapt to new environmental conditions or hosts. The presented data shed some light on TBRV evolutionary dynamics and epidemiology.

Environmental waters, e.g. rivers, lakes and irrigation water, are a good source of many plant viruses. The pathogens can infect plants getting through damaged root hairs or small wounds that appear during plant growth. First results demonstrated common incidence of Tobacco mosaic virus (TMV) and Tomato mosaic virus (ToMV) in water samples collected from irrigation ditches and drainage canals surrounding fields in Southern Greater Poland. Principal objective of this work was to examine if environmental water might be the source of viruses infective to cereals. The investigation was focused on mechanically transmitted pathogens. Virus identification was performed by biological, electron microscopic, serological and molecular methods. Preliminary assays demonstrated Brome mosaic virus (BMV) infections in symptomatic plants inoculated with 9 out of the 17 tested concentrated water samples. The final identification was confirmed by molecular methods for selected isolates named: BMV-Ch1, -DBS, -N, -R and -S. Partial coding sequences of polymerase 1a (RNA1) and 2a (RNA2) and complete nucleotide sequence of coat protein (CP) gene (RNA3) of each BMV isolate were determined and compared with corresponding sequences of other known BMV isolates.Results confirmed the highest amino acid sequence homology in the fragment of polymerase 2a (99.2% -100%) and the most divergence in CP (96.2% -100%). This is the first report on the detection of an infective cereal virus in aqueous environment.

Here we describe two Brome mosaic virus (BMV) isolates from the Wielkopolska region of Poland. The BMV-Sr and BMV-Sz isolates were collected from maize [Zea mays L. ssp. Indentata] and triticale [× Triticosecale Wittm. ex A. Camus] plants respectively. Newly emerged BMV isolates, similarly to the BMV-M2 strain derived from an Arkansas isolate, have a wide host range that includes species in the Poaceae and Fabaceae families. Furthermore, immunological reactions of icosahedral virions from non-inoculated cowpea [Vigna unguiculata L.] leaves with a specific immunoglobulin confirmed that each of these isolates can systemically infect cowpea. We characterized the BMV-Sr and BMV-Sz genomic sequences encoding the replication protein (1a), polymerase (2a), complete movement protein (3a) and coat protein (CP) genes. The 1a, 2a, 3a and CP gene sequences showed 98.9, 97.6, 98.4 and 97.7 % nucleotide sequence identity between the Polish isolates respectively. Phylogenetic analysis based on these four genes confirmed the species identity of the isolates. A phylogenetic tree based on RNA3 (3a and CP genes) showed independent clustering of the Polish isolates. Amino acid sequence analysis of the 3a protein revealed that both Polish isolates are characterized by a single amino acid mutation at the 81st position, when compared with the Russian isolate. It had been previously reported that four amino acid mutations in this region determined BMV systemic infection in cowpea. Our results indicate that a single non-synonymous substitution in the cell-to-cell movement protein may be crucial for the nature of cowpea infection.

The virus in naturally infected, stunted triticale plants was identified as soil‐borne wheat mosaic virus (SBWMV). The infected plants were collected in the Southern Wielkopolska region (Western Poland). Molecular analysis including RT‐PCR, and sequencing of the complete coding sequence of coat protein gene, was performed. The sequence of the Polish isolate of SBWMV (SBWMV‐Pol1) shared 100, 99 and 98% identities with the corresponding regions of De1 (AF519799), OKL‐1 (X81639) and US‐Nebraska (L07938) isolates of SBWMV, respectively. Phylogenetic analyses showed that the Polish isolate, SBWMV‐Pol1, clustered together with other SBWMV isolates. This is the first report of the occurrence of SBWMV in Poland and the second of its presence in Europe.

No abstract