K. Izadpanah

Comparison of a beet curly top virus isolate originating from the old world with those from the new world

The complete nucleotide sequence of an infectious, insect-transmissible clone of a beet curly top virus isolate originating from Iran (BCTV-I) has been determined. The nucleotide sequence of BCTV-I shows high levels of similarity to the sequences of BCTV strains isolated from North America, and is nearly identical to the CFH strain of BCTV. The symptoms produced by BCTV-I in Nicotiana benthamiana and Beta vulgaris most closely resemble those of the CFH strain and are distinct from the other isolates. The significance of these findings with respect to the possible geographic origins and evolution of BCTV are discussed.

The inheritance of resistance to beet necrotic yellow vein virus (BNYVV) in B. vulgaris subsp. maritima, accession WB42: Statistical comparisons with Holly-1-4

In this study, the inheritance of resistance to Beet necrotic yellow vein virus (BNYVV) in accessions Holly-1-4and WB42 was investigated. Crosses between both resistant sources and susceptible parents were carried out and F1F2 and BC1 populations were obtained. Virus concentrations in WB42and its F1 populations were lower than in Holly-1-4. Observed ratios of susceptible and resistant plants in segregating populations of Holly-1-4 as well as WB42 were in agreement with hypothesis of one dominant major gene. Segregation of plants in F2 populations obtained from crosses betweenHolly-1-4 and WB42 revealed that the resistance genes in Holly-1-4 and WB42 were nonallelic and linked loci.

Analysis of nucleotide sequence of Iranian maize mosaic virus confirms its identity as a distinct nucleorhabdovirus

The nucleotide sequence of the Iranian maize mosaic rhabdovirus (IMMV) was obtained using a random-PCR method (rPCR) followed by PCR with specific primers. Analysis of the complete nucleotide sequence of the IMMV genes and intergenic regions comprising a total of 12,381 nucleotides (including the partial sequences of leader and trailer regions) revealed six open reading frames (ORF) on the viral complementary RNA (vcRNA). On the basis of its similarities to other rhabdovirus sequences, the IMMV genome consists of 3′-leader-N-P-3-M-G-L-5′-trailer. The intergenic regions contained a characteristic consensus sequence, 3′-AAUUCUUUUUGGGUUU/G-5′. The IMMV gene products showed a high similarity to those of maize mosaic virus and taro vein chlorosis virus and a more distant relationship to other rhabdoviruses. Together with the biological, serological and morphological features described earlier, our molecular data provide evidence that IMMV is a distinct member of the genus Nucleorhabdovirus in the family Rhabdoviridae.

Characterisation of cineraria strain of Tomato yellow ring virus from Iran

A tospovirus isolated from naturally infected cineraria plants in commercial greenhouses in Shiraz, Iran, induced rings and chlorotic and necrotic spots on leaves, growth reduction and death of the plants. The viruswas transmitted by three populations of Thrips tabaci. Antisera were produced against purified virions and viral nucleocapsids and used to study the virus host range and relationships. On the basis of enzyme-linked immunosorbent assay, tomato, anemone, Arum sp., dandelion and pepper were natural hosts of the virus. SDS-PAGE revealed three major structural proteins corresponding to the Tospovirus N, G1 and G2 proteins. Three RNA segments were resolved in a 1% agarose gel with molecular masses of 1.02×106 Da, 1.87×106 Da and 2.86×106 Da, corresponding to the virus S, M and L RNAs, respectively. No serological relationships were detected between the cineraria virus and Tomato spotted wilt virus, Tomato chlorotic spot virus and Groundnut ring spot virus using the virus nucleocapsid IgG in dot immunobinding assays. Further characterisation by nucleotide sequencing of the virus N gene revealed that it was a strain of Tomato yellow ring virus, although the cineraria isolate appears to have a different experimental host range compared to tomato isolates of the virus.

Characterisation of a strain of Potato virus Y causing eggplant mosaic in southern Iran

Mosaic disease of eggplant (Solanum melongena L.) iscommonin many fields of southern Iran.Avirus isolated from diseased plants in the Boushehr Province was characterised by biological, serological, physiochemical and molecular studies. The virus was mechanically transmissible to Nicotiana tabacum cv. Turkish and several other solanaceous species and to Chenopodium amaranticolor and C. quinoa. Purified preparations of the virus contained flexuous rod-shaped particles. Two aphid species, Myzus persicae and Aphis gossypii, transmitted the virus between Turkish tobacco plants. An antiserum raised against purified virus preparation was used in the detection of the virus. Molecular weights of the virus genome and the coat protein (CP) were estimated at 3.1–3.2×106 and 36×103 Da, respectively. The 3′ region of the virus genome, including the CP and the untranslated region (UTR), was amplified using two pairs of general primers of the family Potyviridae. Sequence information identified the virus as a strain of Potato virus Y (PVY), designated eggplant strain of PVY (PVY-Eg), with the highest sequence homology to a tomato strain of PVY (PVY-LY84.2) from Spain, and a somewhat lower homology to an Indian isolate of Eggplant mottle virus belonging to the PVYO subgroup. Cluster dendrograms based on CP amino acid and 3′UTR sequences placed PVY-Eg within the PVYNP subgroup. This is the first report on the characterisation of a PVYNP strain infecting eggplant in Iran.

Widespread occurrence and molecular characterization of Wheat dwarf virus in Iran

Wheat dwarf virus (WDV), genus Mastrevirus, was associated with yellowing and dwarfing of wheat and barley in many parts of Iran. The complete nucleotide sequence of a barley isolate of the virus consisted of 2733 nucleotides and was most similar to barley isolates of WDV from Turkey, Czech Republic and Germany, but different enough to be regarded as a new strain of the virus. Phylogenetic analysis indicated that mastreviruses causing yellows and dwarfing in wheat and barley form two distinct groups. The Iranian and European barely isolates fall in one group while all wheat isolates are placed in another group. These results confirmed the division of WDV isolates into two distinct strains. WDV was also found in mixed infection with barley yellow dwarf viruses (BYDVs) in barley and wheat plants. Using dot blot hybridization with the full ssDNA genome of the Iranian barley isolate of WDV as a probe and PCR with primers which amplified the full length DNA of the virus, WDV was detected in 46 of 211 BYDV positive barley and wheat samples from northern, northwestern, northeastern, central and southern Iran. It is concluded that in addition to BYDVs, WDV is a major component of the yellows complex in cereal fields in Iran.

A new strategy for generating geminivirus resistant plants using a DNA betasatellite/split barnase construct

The betasatellite DNA associated with cotton leaf curl disease contains a single ORF, βC1, which is a pathogenicity determinant. Deletion of the βC1 ORF showed that it was not required for betasatellite replication in the presence of Tomato leaf curl virus-Australia (TLCV-Au). A series of betasatellite/split mutant barnase gene constructs, in which a direct repeat of the Bacillus amyloliquefaciens barnase gene flanked the betasatellite, were shown to replicate in tobacco in the presence of TLCV-Au. A betasatellite/split intact barnase gene construct, with the optimal direct repeat unit of the barnase gene, was introduced into Nicotiana tabacum plants. Approximately one third of the transgenic lines containing the betasatellite/split barnase gene constructs were shown to be completely resistant to the TLCV-Au infection. The betasatellite/split intact barnase gene cassette ensures that there is no expression of the barnase in the absence of TLCV-Au, but upon infection of the cell with the virus, release of the betasatellite/split barnase cassette as a replicating molecule resulting in the reconstitution and expression of an active barnase gene and the destruction of the infected cell. This system offers the potential to provide resistance in a variety of plant species against geminiviruses that support the replication of betasatellite.

Characterisation of lettuce virus X, a new potexvirus infecting lettuce in Iran.

A virus with flexuous rod-shaped particle morphology was found in samples from lettuce during a survey of viruses infecting lettuce in Tehran province in Iran. This virus was subjected to a complete analysis of its biological and molecular features. The entire nucleotide sequence of the virus was determined, revealing a polyadenylated ssRNA genome consisting of 7,212 nucleotides [without poly (A) tail] and possessing an organization typical for potexviruses. Comparative genome analysis showed that the lettuce virus is closely related to Alstroemeria virus X, narcissus mosaic virus and asparagus virus 3. Based on particle morphology, physico-chemical properties and the complete genome sequence, this virus is a member of a new species in the genus Potexvirus, for which the name lettuce virus X (LeVX) is proposed. Biological assays using an infectious cDNA clone and a wild-type isolate of LeVX revealed that the virus, despite reaching high concentrations in all lettuce cultivars tested, does not cause symptoms in lettuce.

Molecular characterization of Iranian wheat stripe virus shows its taxonomic position as a distinct species in the genus Tenuivirus

Summary.The full lengths of three genome segments of Iranian wheat stripe virus (IWSV) were amplified by reverse transcription (RT) followed by polymerase chain reaction (PCR) using a primer complementary to tenuivirus conserved terminal sequences. The segments were sequenced and found to comprise 3469, 2337, and 1831 nt, respectively. The gene organization of these segments is similar to that of other known tenuiviruses, each displaying an ambisense coding strategy. IWSV segments, however, are different from those of other viruses with respect to the number of nucleotides and deduced amino acid sequence for each ORF. Depending on the segment, the first 16–22 nt at the 5′ end and the first 16 nt at the 3′ end are highly conserved among IWSV and rice hoja blanca virus (RHBV), rice stripe virus (RSV) and maize stripe virus (MStV). In addition, the first 15–18 nt at the 5′ end are complementary to the first 16–18 nt at the 3′ end. Phylogenetic analyses showed close similarity and a common ancestor for IWSV, RHBV, and Echinochloa hoja blanca virus (EHBV). These findings confirm the position of IWSV as a distinct species in the genus Tenuivirus.

FIRST REPORT OF A 16SrIX GROUP (PIGEON PEA WITCHES'-BROOM) PHYTOPLASMA ASSOCIATED WITH GRAPEVINE YELLOWS IN IRAN

Association of 16SrXII-A phytoplasmas with grapevine yellows (GY) has been previously reported from Fars and Lorestan provinces of Iran (Salehi et al., 2014). During 2013-2014 surveys, symptoms resembling those of GY disease including thickening and downward rolling of leaves, vein chlorosis and necrosis, shoot dieback and stunting were observed in vineyards of Shiraz area (Fars province, Iran). Total DNA samples extracted from eight symptomatic and eight symptomless vines were tested for phytoplasma presence. In direct PCR using primers P1/P7 and nested PCR using primer pairs P1/P7 followed by R216F2n/R16R2 (Lee et al., 1998), respectively amplicons of ca. 1.8 and 1.2 kb were amplified from symptomatic but not from symptomless vines. Samples that yielded P1/P7 amplicons (4/8) were cloned and sequenced; obtained sequences showed 100% identity. A BLAST search using full length 16S rRNA gene sequence of a representative of these sequences (GenBank Accession No. KX011516) revealed that the sequence shared 99% homology with Indian Brassica rapa phyllody phytoplasma (HM988986), a representative of 16SrIX-C subgroup. Computer-simulated restriction analysis using iPhyClassifier showed that the RFLP profile of the Shiraz GY (SGY) phytoplasma 16S rDNA sequence was identical (similarity coefficient 1.00) to Picris echioides yellows phytoplasmas (Y16389) representative of subgroup C of the 16SrIX group. Phylogenetic analysis revealed that SGY phytoplasma clustered with16SrIX group phytoplasmas closer to Indian B. rapa phyllody phytoplasma, a 16SrIX-C member. To our knowledge, this is the first report of natural infection of grapevine by a 16SrIX phtoplasma in Iran.