Cereal-infecting Mastreviruses are one of the most ubiquitous of viruses, having caused huge yield losses during the last decade in the Czech Republic. The presence of two strains of Wheat dwarf virus (WDV), one of which is wheat adapted and one barley adapted, have been confirmed from among field samples of wheat and barley plants. The virus typing was conducted by both PCR-RFLP and sequencing-based methods. The Czech WDV isolates of the barley strain are more variable than the isolates of the wheat strain, separating them into two clades, one representing a pool of divergent isolates. The RFLP analysis confirmed the separation of the Czech isolates into two strains and highlights a powerful method for the rapid diagnosis of both the wheat and barley strains. Additionally, both RFLP and sequence analysis have shown that the barley strain is restricted to the barley host, while the wheat strain is present in both wheat and barley plants.

The tritimovirus Wheat streak mosaic virus (WSMV) is widespread throughout the world and represents a severe threat to cereal crop production. To increase knowledge of genetic diversity of WSMV in Europe, until now scarce, capsid protein (CP) sequences of several Czech, French, Italian, Slovak, and Turkish isolates have been determined. A multiple alignment of CP nucleotide sequences using available WSMV sequences revealed only limited sequence variation among 3 previously sequenced European isolates and the 14 European isolates sequenced in this study. Moreover, these isolates were characterized by an identical 3-nucleotide deletion, resulting in the lack of the Gly2761 codon within the CP region of the polyprotein. The results indicate that this monophyletic group of isolates (designated as WSMV-ΔE) is common and widely dispersed throughout the European continent. The close relationship of WSMV-ΔE isolates implies a single common ancestor and, presumably, subsequent dispersal throughout Europe from a single focus. We developed two simple assays for specific and accurate detection of WSMV-ΔE isolates. First, a conserved ClaI restriction site in the core CP gene sequence unique to WSMV-ΔE isolates was used for restriction fragment length polymorphism analysis of amplified polymerase chain reaction (PCR) products. Second, the conserved and specific codon gap in WSMV-ΔE sequences was used as a target to design specific primers functional in one-step reverse-transcription PCR detection of WSMV-ΔE isolates.

A rapid method for detection, discrimination and quantification of wheat and barley strains of wheat dwarf virus (WDV) was successfully developed. The sensitivity of quantification of the wheat and barley strains of WDV ranged from an average of 1.2 × 10(7)-1.2 × 10(2) and from an average of 1.4 × 10(7)-1.4 × 10(4) copies of viral genome, respectively. These standard serial dilutions were applied to plant and vector tissues for virus titer calculations. Both strains of WDV were clearly discriminated by specific probes and melting curve analysis. Both TaqMan(®) and SYBR(®) Green technologies provided accurate and reliable methods for monitoring, detection, discrimination, and quantification of WDV.

No abstract

Plum pox virus (PPV), the causal agent of Sharka disease, is an important pathogen of stone fruit trees. In this study, 24 new Czech PPV isolates from five different orchards were collected and characterized, molecularly. PPV-D isolates were identified in all orchards studied; whereas PPV-Rec isolates were identified in only two of them. A phylogenetic analysis on (Cter) NIb-(Nter) CP was performed. Three Czech PPV-D isolates BOH11CZ, BOH12CZ, and BOH13CZ diverged into a significantly separated cluster. PPV-Rec isolates formed a fairly homogenous group. However, the Bohutice and the Lipov PPV-Rec isolates clustered in two significantly separated branches.