Department of Plant Pathology, College of Agriculture and Natural Resources, Science and Research Branch, Islamic Azad University, Tehran 14515-775, Iran
Department of Plant Virology, Plant Pests and Diseases Research Institute, P.O. Box 19395-1454, Tehran, 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.