Members of the family Closteroviridae have been traditionally defined as plant viruses with thread-like particles having messenger-sense single-stranded RNA, the largest genomes among RNA plant viruses. Individual virus species are distributed worldwide and some of them cause devastating crop losses. The natural host range usually narrow. Diseases symptoms are yellowing type or pitting and/or groowing of the woody cylinder. Infection systemic, but usually limited to the floem. Natural vectors are aphids, whiteflies, pseudococcids, coccids and mealybugs. Transmission is semipersistant. Closteroviruses contains 9-13 ORFs flanked by 5'- and 3'- untranslated regions with different length. The genome strategy is based on polyprotein precessing, +1 ribosomal frameshift and formation of subgenomic RNAs. Common features of closteroviruses that encode a homologue of HSP70 molecular chaperones found in all cells (HSP70h) and a duplicate (CPd) of the coat protein gene.
Virus symptoms were observed on Hedge bindweed (Calystegia sepium) a well known plant in Hungary. In the literature there is no record of virus infection on Hedge bindweed, therefore, investigations were carried out to determine the causal agent. Sap from leaves showing virus-like symptoms was inoculated onto test plants inducing systemic infection on Nicotiana clevelandii, N. benthamiana, local lesions on Chenopodium quinoa and no infection on Datura stramonium and Cucumis sativus. Sap of N. clevelandii was examined by electron microscopy, showed the presence of long flexous particles. The biological and other properties of the virus have also been studied. Properties of particles in sap were as follows: TIP (thermal inactivation point): 78 °C, LIV (longevity in vitro): 26 days and DEP (dilution end point): log 10 minus 5. The size of coat protein is 36 kDa, and the genome consists of 7-8000 nt RNA. Double-stranded cDNA were produced using random hexanucleotide primers, cloned and sequenced. BLAST search of sequence databases revealed nucleotide sequence identity with carlaviruses. Further investigations are needed to decide whether the virus isolated from Hedge bindweed is a new carlavirus or a new strain of an existing carlavirus.
Two wheat-infecting isolates of WDV-WDV-B and WDV-F-
were collected in the field of Martonvásár and Nagykovácsi.
The complete genomes were amplified by PCR, cloned into pBKS+ plasmid and
sequenced. The nucleotide divergence in the total genome of the five isolates-WDV- Fra, WDV-Cz, WDV-Swe, WDV-B and WDV-F-originating from different part of Europe were found to be
0.44-1.69%. The four genes-
MP, CP, RepA and Rep-and two non-coding region-LIR and SIR-
were compared and a phylogenetic tree was constructed.
Planococcus citri (Risso, 1813) and Planococcus ficus (Signoret, 1875) (Hemiptera: Pseudococcidae) are important polyphagous pests species. Their high degree of morphological similarity in male and larval stage makes them difficult to distinguish. The aim of the study was to find a simple and fast PCR-based method to separate these two mealybug species. Thanks to the use of a short DNA extraction method and species-specific primer pairs, P. citri and P. ficus can be distinguished at any developmental stages within three hours.
The Fabaceae species Lathyrus tuberosus, Vicia species and Coronilla varia, all of which have an extended flowering period, provide the larvae food and shelter long enough for the pea thrips Kakothrips pisivorus to complete its development, and to have two generations yearly. Although flowers of pea cultivars also confer suitable conditions for egg laying, their flowering period is rather short. Therefore, the larvae are forced to move to developing pea pods in damaging numbers, resulting in the development of only one generation yearly on pea. However, specimens of K. pisivorus are able to colonize pea cultivars that have a similar phenology as Lathyrus tuberosus. Here we show that Hungarian pea thrips populations having either one or two generations are genetically identical.
Authors:I. Tóbiás, N. Bakardjieva, and L. Palkovics
Maize dwarf mosaic is the most widespread virus disease affecting corn production in Hungary and Bulgaria. Samples from virus infected maize were collected from different part of Bulgaria and employed test plants, ELISA serological method and RT-PCR in order to identify the viral pathogen.
Maize dwarf mosaic virus
(MDMV) was detected in all tested samples. For further investigation three MDMV isolates were selected and cloned. Cloned cDNAs representing the coat protein gene of the virus have been sequenced. The coat protein genes of Bulgarian and Hungarian isolates of MDMV were compared. The nucleotide sequence identity and amino acid sequence similarity of the coat protein region varied from 88% to 99.1% and from 95.1% to 99.6%, respectively. The N-terminal region of coat protein was compared with other members SCMV subgroup and phylogenetic tree was constructed.
Authors:A. Almási, I. Tóbiás, I. Manoussopoulos, Zs. Basky, and L. Palkovics
Nucleotide and amino acid sequences of the helper component protease (HC-Pro) and the coat protein (CP) of two Hungarian
Potato virus Y
(PVY) isolates, differing in aphid transmissibility were determined. Isolate PVY-5 belongs to the common “O” strain (PVY
), whereas isolates PVY-98 and PVY-111 belong to the “N” (PVY
) and the PVY-NTN and PVY-H to the “NTN” (PVY
) strains, respectively. The PVY-5 isolate varied significantly from the others in aphid transmission and in the ability to systemically infect potato plants. To elucidate whether these differences were due to mutations affecting known functional motifs, the corresponding cistrons of the two proteins were sequenced and aligned. Our analysis showed that none of the well-known motifs, responsible for aphid transmission in the two proteins had been affected. However, the defective isolate had two natural mutations in the HC-Pro in the vicinity of the PTK motif, and a number of mutations in the CP, distributed both in the N-terminus and the central region. As these two proteins are the only known viral participants in the aphid transmission mechanism, it is likely that some of the observed mutations might be involved in this process. Thus, our results indicate that other, previously unidentified sequences or factors may influence virus-vector interactions and transmission of PVY.
Authors:A. Künstler, L. Király, M. Pogány, I. Tóbiás, and G. Gullner
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.
Authors:I. Tóbiás, B. Kiss, K. Salánki, and L. Palkovics
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
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).
Authors:G. Bozsik, A. Lakatos, G. Szőcs, and I. Tóbiás
The European corn borer moth, (ECB), Ostrinia nubilalis
(Lepidoptera: Crambidae, Pyraustinae) is one of the most destructive pests of
maize worldwide. ECB has two pheromone-strains, separated by specific ratios of
isomers of E- and Z11-tetradecenyl acetates (E11- and Z11-14Ac), but appearing
morphologically identical. Accordingly, E- and Z-ECB pheromone traps are
available for the respective populations for practical monitoring of the flight,
however, traps for Z-strain are unreliable for practical usage in some parts of
Central-Europe. E- and Z-ECB populations occur in sympatry in some areas, while
in allelopatry in other areas. Determining the strains before the flight of
adults, when difference in the composition of their respective pheromones is
manifested, would be of practical interest for early warning. In addition to the
known fatty-acyl-reductase (FAR) marker, further markers would allow more
comprehensive studies. We screened the following common markers for
mitochondrial and nuclear DNA regions: partial cytochrome c oxidase I (COI),
cytochrome B (CytB), the second spacer of the internal transcribed spacer
(ITS2), Elongation factor 1a (EF1a) and actin gene (Act). In addition, a marker
of the Δ11-desaturase gene (11desat), linked to biosynthesis of female-produced
sex pheromone, was also included, because we reported earlier a differential
expression for this site. Three Z-ECB populations locating at distant sites
within Hungary, an area where only Z-strain occurs, and an E-ECB population in
Slovenia, known as the closest-occurring E-strain, were included into the study.
Separate laboratory colonies were established from each population, and
F1 generations were sampled to verify the identity of pheromone
strains, by analysing the composition of sex pheromone by gas chromatography
linked to an electroantennographic detector (GC-EAD). Molecular studies were
conducted using specimens taken from the F2 generations. Results of
genetic studies showed that there were no differences between the Z and E
populations for the common markers. In contrast to this, several nucleic acid
changes (11 nt in 4 positions) were found between the three Z-populations
(Hungary) and the E-population (Slovenia) in the desaturase marker. Further
study is required to reveal whether the differences found in this study are
consistent across E-populations, thus making these markers suitable for