RESUMO
A distinct isolate (TY-PF36) of Tomato yellow fruit ring virus (TYFRV) was obtained from potato (Solanum tuberosum) in Iran. Chlorosis and necrotic spots on leaves associated with leaf and stem necrosis symptoms appear on the affected plants. Of 32 plant species and cultivars mechanically inoculated, 24 were susceptible to the virus isolate. The isolate strongly reacted with TYFRV antibodies in enzyme-linked immunosorbent assay (ELISA), but not with the specific antibodies of other tospoviruses tested. TYFRV-specific N gene primers described previously, however, failed to produce DNA fragments from the total RNA extracts of the infected plants in reverse transcription-polymerase chain reaction (RT-PCR). Nucleotide sequencing of the complete N gene and partial L gene of this isolate revealed considerable differences to those reported for TYFRV with identities ranging from 83.9 to 84.2% and 84.9 to 85.4%, respectively. Two specific primers were designed for detecting TY-PF36 using RT-PCR; TY-PF36 was detected in symptomatic field samples of potato, peanut, soybean, and two weed species, Datura metel and D. stramonium.
RESUMO
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.
