Ambient conditions of elevated temperature and CO2 levels are detrimental to the probabilities of transmission by insects of a Potato virus Y isolate and to its simulated prevalence in the environment.

Conditions of elevated temperature and CO2 levels [30 °C and 970 parts-per-million (ppm), respectively] reduced the systemic titers of a potato virus Y (PVY) isolate in Nicotiana benthamiana plants, relative to standard conditions (25 °C, ~405 ppm CO2). Under controlled conditions we studied how these growing environments affected the transmission of infection by aphids. Probabilities of transmission of infection by insects that fed on infected donor plants kept at either standard conditions, or at 30 °C and 970 ppm CO2 were both determined and found to positively correlate with titers in donor leaves, independently of the ambient conditions in which recipient plantlets would grow. With these data, viral prevalence was simulated under conditions of elevated temperature and CO2 levels and found that for it to remain comparable to that simulated under standard conditions, insect arrivals to recipient plants in the former scenario would have to increase several-fold in their frequency.

Prevalence and genetic diversity of fig mosaic virus isolates infecting fig tree in Iran.

Commercial and outdoor fig orchards in four Iranian provinces were surveyed for the incidence of fig mosaic virus (FMV), fig leaf mottle associated virus 2 (FLMaV-2) and fig mild mottle associated virus (FMMaV) from March 2011 to October 2012. A total of 350 asymptomatic and symptomatic fig samples were collected and tested by dot-immunobinding assay (DIBA) for the fig mosaic disease (FMD) using a polyclonal antiserum. According to DIBA results, FMD was present in 73% of the collected symptomatic samples from all visited regions. Samples with positive reactions in DIBA were then analyzed by RT-PCR using with specific primers. PCR results showed that about 14.8% of the FMD-positive samples from three inspected provinces are infected with at least one virus. FMV was the most widely spread virus (14%) followed by FLMaV-2 (1.5%), whereas FMMaV was not found. Phylogenetic analysis of the glycoprotein nucleotide and amino acid sequences of known FMV isolates showed two independent groups with high bootstrap values, with all Iranian isolates distinctly clustered in group I, subgroup IA beside those reported in Turkey. Nucleotide diversity was high within but low between different selected geographic regions and except for Europe, nucleotide distance within geographic regions was low. Statistical analyses indicated a correlation between the genetic structure of the FMV isolates and the geographical origin of isolation. Our analyses suggested that the FMV population is in a state of increase following a bottleneck or founder event in Iran.

Genetic diversity, host range, and distribution of tomato yellow leaf curl virus in Iran.

Tomato yellow leaf curl virus (TYLCV) is considered one of the most important tomato pathogens in tropical and subtropical regions including Iran. During the years 2007 to 2009, a total number of 510 symptomatic and asymptomatic vegetable, ornamental and weed samples were collected from fields and greenhouses in ten provinces of Iran. Symptoms included stunting, yellowing, leaf curl and flower senescence. PCR with specific primers showed TYLCV infection in 184 samples (36%) such as cucumber, pepper, tomato and several weeds from seven provinces. Based on the geographical origin, host range and symptoms, twenty three representative isolates were selected for phylogenetic analysis. An amplicon with a size about 608 base pair (bp) comprising partial sequence of the coat (CP) and movement protein (MP) coding regions of the viral genome was sequenced and compared with the corresponding selected sequences available in GenBank for Iran and worldwide. Phylogenetic analyses on the basis of the nucleotide sequences indicated two geographically separated clades. Isolates collected from Hormozgan, Khuzestan and Kerman provinces were grouped together with other Iranian isolates including TYLCV-Ir2, TYLCV-Kahnooj, and an isolate from Oman. It was also revealed that isolates collected from Boushehr, Fars, Tehran, and Isfahan placed close to the Iranian isolate TYLCV-Abadeh and isolates from Israel and Egypt. No correlation was found between the genetic variation and the host species, but selected Iranian isolates were grouped on the basis of the geographical origins. Results of this study indicated a high genetic diversity among Iranian TYLCV isolates.

First Report of Tomato mosaic virus on Common Sow Thistle in Iran.

The natural incidence of Tomato mosaic virus (ToMV) in common sow thistle (Sonchus oleraceus) from vegetable fields was assessed to determine the role of this weed species as a virus inoculum source. Twenty sow thistle plants with virus-like foliar symptoms including mosaic and malformations were collected from five vegetable fields in Tehran province, Iran, and analyzed by double antibody sandwich (DAS)-ELISA for the presence of ToMV, Tobacco mosaic virus (TMV), and Cucumber mosaic virus (CMV) using specific polyclonal antibodies (Agdia, Elkhart, IN). Six out of the 20 sow thistle plants tested by ELISA were infected with ToMV. This virus was detected in three of five vegetable fields surveyed, while CMV and TMV were not detected. Mosaic symptoms were associated with the ToMV infection, similar to those caused by TMV in common sow thistle in Iran (2). Viral infection was confirmed by RT-PCR using previously described specific primers to amplify a region in the coat protein gene of ToMV (3). The RT-PCR resulted in the amplification of an expected fragment of ~480 bp from ToMV-infected but not from healthy plants. The nucleotide sequence of the amplified DNA fragment was purified (GeneJET Gel Extraction Kit, Fermentas, Germany), directly sequenced, and deposited in GenBank as Accession No. KF527464. BLAST analysis showed 95 to 97% and 98 to 100% identity at the nucleotide and amino acid levels, respectively, with comparable sequences of other ToMV isolates (GenBank AF062519, FN985165, GQ280794, and JX857634). Mechanical inoculation of sow thistle plants with sap of symptomatic sow thistles reproduced symptoms of field-infected sow thistles. The presence of ToMV in the inoculated plants was confirmed by ELISA and RT-PCR. This suggested that ToMV could be the causal agent of the disease on sow thistle. In our earlier studies, the distribution and genetic diversity of ToMV isolates infecting vegetable crops and weed plants were studied (1); however, to our knowledge, this is the first report of ToMV infecting common sow thistle in Iran. References: (1) V. Aghamohammadi et al. J. Plant Pathol. 95:339, 2013. (2) A. Alishiri et al. Plant Pathol. J. 29:260, 2013. (3) B. Letschert et al. J. Virol. Methods 106:10, 2002.

First Report of Tomato ringspot virus Infecting Pepper in Iran.

Chili pepper (Capsicum frutescens) represents an important crop in Iran and is under cultivation in different regions in Northern Iran. In spring 2012, commercially grown tabasco (Capsicum frutescens) peppers in Varamin, Shahriar, and Karaj districts of Tehran province developed an undescribed disease. Symptoms observed were mosaic, leaf malformations, and stunting. Fruit symptoms included chlorosis and distortion. To verify the identity of the disease, six fields were surveyed and 72 symptomatic leaves were collected and screened by double antibody sandwich (DAS)-ELISA using specific antibodies to Tobacco ringspot virus (TRSV), Tomato ringspot virus (ToRSV), Pepper mild mottle virus (PMMV), Tomato mosaic virus (ToMV), Tobacco mosaic virus (TMV), and Arabis mosaic virus (ArMV). ToRSV was found in 23% of the samples collected. None of the samples had a positive reaction to other tested viruses. The ToRSV-positive peppers were used for mechanical transmission to Chenopodium quinoa, local lesion host, and after two cycles of single local lesion isolation, they were transferred to Cucumis sativus, Solanum esculentum, and Capsicum fructescens. Inoculations resulted in systemic mosaic and chlorotic local lesion on C. sativus; leaf distortion and mosaic on S. esculentum; and mosaic, mottle, and stunting on C. fructescens. All inoculated plants were positive for ToRSV with DAS-ELISA. To further verify ToRSV infection, reverse transcription (RT)-PCR was conducted. Two primers were designed on the basis of the highly conserved sequences of the putative viral polymerase gene available in the GenBank. RT-PCR of total RNA extract from infected peppers and inoculated plants with the designed primers RdR-R (5'-CGCCTGGTAATTGAGTAGCCC-3') and RdR-F (5'-GAAGAGCTAGAGCCTCAACCAGG-3'), consistently amplified the 411-bp product, while no amplification products were obtained from noninfected control (healthy plants). The fragment from tabasco pepper was cloned into pTZ57R/T (Ins T/A clone PCR Cloning kit, Fermentas, St. Leon-Rot, Germany) and sequenced in both directions of three clones. The resulting nucleotide sequence (GenBank Accession No. JQ972695) had the highest identity (94%) with the polymerase gene of a ToRSV isolate from blueberry cv. Patriot (Accession No. GQ141528) and had lower identity (91%) with that of a ToRSV isolate from blueberry cv. Bluecrop (Accession No. GQ141525). Tomato ringspot virus (ToRSV) is reported to infect Capsicum spp. in the United States (1,2). Our results confirm the natural infection of pepper plants in Tehran by ToRSV. To our knowledge, this is the first report of ToRSV infection of pepper in Iran. The finding of this disease in Tehran confirms further spread of the virus within northern regions of Iran and prompts the need for research to develop more effective management options to reduce the impact of ToRSV on pepper crops. Beside, primers designed on the basis of putative viral polymerase gene sequences may improve the detection of ToRSV isolates by RT-PCR in Iran. References: (1) S. K. Green and J. S. Kim. Technical Bulletin. No.18, 1991. (2) G. P. Martelli and A. Quacquarelli. Acta Hortic. 127:39, 1983.

Occurrence of Prunus necrotic ringspot virus and Arabis mosaic virus on Rose in Iran.

Rose is an economically important crop for Iran and the world. A survey was carried out from March 2005 to January 2006 to identify viruses infecting rose plants (Rosa × damascena, R. chinensis, R. canina, R. indica, and R. multiflora) in five plantations (Damavand, Tehran, Karaj, Shahre-Rey, and Varamin) in and near the Tehran Province of Iran. Samples (526) from eight rose-growing plantations were collected. All samples were tested for Prunus necrotic ringspot virus (PNRSV), Arabis mosaic virus (ArMV), and Cucumber mosaic virus (CMV) using the dot-immunobinding assay (1) and double-antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) according to the manufacturer's instructions (Bioreba, Basel, Switzerland). Among the samples tested, PNRSV and ArMV were found in 23.1 and 18.8% of the collection, respectively. No CMV was detected in any of the samples. The presence of ArMV and PNRSV was verified in samples by transmission to indicator test plants, cucumber (Cucumis sativus), French bean (Phaseolus vulgaris), and Cowpea (Vigna unguiculata). Inoculation with extracts from PNRSV-positive plants produced systemic mosaic, stunting, and vein banding on cucumber, and necrotic local lesions on cowpea. No symptoms were observed in French bean. Inoculation with extracts from ArMV-positive plants produced systemic vein banding on cucumber, chlorotic local lesions on French bean, and systemic mosaic on cowpea. These symptoms were similar to those that were described previously for these viruses (2,4). The symptoms observed on indicator plants for each virus corresponded to the results of DAS-ELISA. Examination of crude sap prepared from ArMV- and PNRSV-infected cucumber leaves using immu-nosorbent electron microscopy (IEM) revealed the presence of isometric virus particles with a diameter of approximately 30 and 25 nm, respectively. Frequencies of occurrence of these two viruses as determined by serological detection showed ArMV to be the most prevalent virus in high altitudes (1,700 to 1,900 m above sea level) compared with the lowland regions. Serological tests also indicate that PNRSV is mostly distributed through the red rose varieties (Rosa × damascena, R. chinensis, R. canina, and R. multiflora) and ArMV is within the white varieties (R. canina, R. indica, and R. multiflora). However, mixed infections of PNRSV and ArMV were detected in all rose samples tested. An infection by PNRSV and ArMV either singly or in combination is usually responsible for rose mosaic disease. PNRSV has been isolated in many rose-growing regions worldwide. ArMV alone or in complexes with ilarviruses infect garden and greenhouse rose in Europe and India (3). Mosaic is probably the most commonly found virus on roses. To our knowledge, this is the first report of a natural occurrence of ArMV and PNRSV on rose in Iran. References: (1) E. E. Banttari and P. H. Goodwin. Plant Dis. 69:202, 1985. (2) M. Boulila and M. Marrakchi. Phytopathol. Mediterr. 40:125, 2001. (3) S. Kulshrestha et al. Curr. Sci. 89:1759, 2005. (4) N. Salem et al. Plant Pathol. 86:85, 2004.