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  • Author or Editor: I. Tóbiás x
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Barley-infecting isolates of Wheat dwarf virus (WDV) were collected in the field in the vicinity of the cities Dunakiliti, Heves and Siófok, in Hungary. Viral genomic DNA was amplified by the rolling circle amplification technique, digested with Hind III, cloned into pBSK+ plasmid and sequenced. The clones were of the same size and showed above 99% identity to each other. Based on DNA sequences WDV-D01, WDV-H1 and WDV-H07 isolates showed high identity (94–99%) to isolates of WDV barley strain and Barley dwarf virus and lower identity to Oat dwarf virus (71% identity) and WDV wheat strains (85% identity).

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Barley-infecting isolates of WDV were collected in the field of near Sofia. The complete genomes of two isolates were amplified by PCR, cloned into pGEM-T plasmid and sequenced. The two clones were the same size and showed complete homology. The WDV-Bg17 clone was compared with Barley dwarf virus, Oat dwarf virus and Wheat dwarf virus isolates. Based on DNA sequences WDV-Bg17 isolate shows high homology (95–97%) to Barley dwarf virus isolates and differs from Oat dwarf virus (71% homology) and Wheat dwarf virus (85% homology).

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Fatty acid hydroperoxide-producing lipoxygenase (LOX) and hydroperoxide-degrading glutathione peroxidase (GPOX) enzyme activities were studied in leaves of virus resistant Xanthi-nc and susceptible Samsun-nn tobacco cultivars after inoculation with Tobacco mosaic virus (TMV). Total LOX activity showed a maximum at pH 5.5 in cell-free extracts of uninfected leaves. LOX activity markedly increased at this pH after TMV inoculation, but a substantial induction was detected also in the basic pH range with an emerging peak around pH = 8.5. TMV-elicited LOX induction was weaker and appeared later in Samsun-nn than in Xanthi-nc leaves. GPOX activity was also substantially induced by TMV infection. However, this induction appeared only 4 days post-inoculation in resistant Xanthi-nc plants in tissues surrounding the localized necrotic lesions. In contrast, GPOX activity did not change in TMV-inoculated, susceptible Samsun-nn leaves. Several glutathione S-transferase (GST) isoenzymes also display GPOX activity. The expression of a tau class GST gene was markedly induced by TMV inoculation in Xanthi-nc leaves. This tobacco GST gene was partially cloned and sequenced.

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