Identification of Tomato Mosaic Virus Infection in Jasmine

Virus-like symptoms were recently observed on leaves of landscape and nursery downy and star jasmine (Jasminum multijlorum) and wax jasmine (J. gracile) in southeast Florida. Foliar symptoms included mottling, chlorotic ring spots and chlorotic line patterns. An agent was mechanically transmitted with difficulty from symptomatic leaves of downy jasmine to Nicotiana debneyi and N. tabacum 'Xanthi' ·and subsequently from these hosts to Chenopodium quinoa and other herbaceous test plants. Virions were isolated from N. tabacum 'Xanthi.' Rod-shaped particles (297 x 18 nm) similar to tobamoviruses were observed in partially purified virus preparations, and in leaf dips from symptomatic star jasmine and indicator plants. Extraction of viral-associated double-stranded (ds) RNA revealed a profile consistent with that of a tobamovirus. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis showed that the virus contained one polypeptide with an approximate molecular weight (Mr) of 18 kDa. The virus reacted specifically with IgG for Tobacco mosaic virus (TMV) and related tobamoviruses [including Tomato mosaic virus (ToMV)] in double antibody sandwich, enzyme-linked immunosorbent assay. No reaction was observed with TMV specific IgG. Reverse transcriptionpolymerase chain reaction with total RNA isolated from symptomatic jasmine leaves and infected N. tabacum 'Xanthi' using ToMV coat protein specific primers amplified the expected product from downy and star (but not wax) jasmine and N. tabacum 'Xanthi.' The nucleotide and amino acid sequence of the products were 100% identical to the corresponding fragment of a Brazilian isolate of ToMV from Impatiens. To our knowledge, this the first report of ToMV in jasmine in the USA. INTRODUCTION Among the different Jasminum species (Oleraceae) , downy and star jasmine (Jasminum multiflorum) and wax jasmine (J gracile) are commercially cultivated and commonly grown ornamentals in Florida. They are popular decorative shrubs widely planted around private gardens and public buildings for their long life, vigor and delicate smell from their flowers. To date, three well-characterized viruses have been identified in different jasmine species, including 1) Tobacco ringspot virus (TRSV) in J. nud~florum, J. mesney and J. officinale (Waterworth. 1971, 1975; Morton, et aI., 1976), 2) Arabis mosaic virus (ArMV) in J. mesney and J. officinale (Waterworth, 1971; Cooper and Sweet, 1976), and 3) Cucumber mosaic virus (CMV) in J. polyanthum (Annual Report of Denmark, 1982). A virus named Jasminium chlorotic ring spot virus (JCRSV) found in J. sambac in India has been reported to be whitefly (Bemisia tabaci) transmitted (Wilson, 1972). In addition, two Proc. XI th IS on Virus Diseases in Ornamentals Ed. C.A. Chang Acta Hort. 722, ISHS 2006 277 more viruses, one called Jasmine mild mosaic from J. multiflorum showing mild mosaic symptoms and the other called Jasmine latent virus 1 from symptomless J. odoratissium, have been isolated on host plants (Waterworth, 1971) but not further characterized. Virus-like symptoms were recently observed on the leaves of landscape and nursery downy, star and wax jasmine plants in southeast Florida. Foliar symptoms included mottling, ring spots and chlorotic line patterns (Fig. 1). The objective of this study was to identify the pathogenes) associated with the disease symptoms observed on downy, star and wax jasmine plants. MATERIALS AND METHODS Plant Material, Inoculation Methods and Host Range Determination Nursery propagated downy, star and wax jasmine plants with foliar symptoms suggestive of virus infection were maintained in a greenhouse. Tissue (leaf, bark and flower) samples from these plants and landscape grown plants were used for mechanical inoculations of herbaceous hosts. Jasmine tissues were triturated with various buffers containing chemicals such as ascorbic acid, caffeine, ethylendiaminetetraacetate (EDTA), nicotine sulfate, potassium cyanide, sodium diethyldithiocarbamic acid, sodium salt (OIECA), sodium sulfite, sodium thioglycolate, 2-mercaptoethanol (2-ME) and gelatin. Such tissue extracts were rubbed onto Carborundum-dusted leaves of herbaceous test plants from Chenopodiaceae and Solanaceae and inoculated leaves were rinsed with tap water. Inoculated plants were held in an air-conditioned greenhouse under natural lighting with a daytime temperature of 24° C and observed for symptom development. Following one of these inoculations, symptoms were observed on Nicotiana debneyi and N. tabacum 'Xanthi' plants. Subsequent mechanical transfer from these Nicotiana plants to a range of herbaceous test plants used leaf tissue triturated in 20 mM sodium phosphate buffer (pH 7.0) containing 1% (wt/vol) Celite. The isolated virus was maintained by serial passages on N. tabacum 'Xanthi' or Chenopodium quinoa Willd. plants. Isolation and Characterization of Double-stranded (ds) RNA and Virions Mechanically transmitted virus was propagated in N. tabacum 'Xanthi' and systemically infected leaves were harvested 14 days after inoculation. OsRNA was extracted from 7-g leaf samples following the protocol of Valverde et al. (1990). DsRNA was analyzed by electrophoresis on native 5% polyacrylamide gels and detected by silver staining. Based on dsRNA analyses, a tobamovirus was suspected and a protocol described by Wetter and Conti (1988) was used for virion isolation. Virus concentration was estimated spectrophotometrically using an extinction coefficient of E260nm 0.1% = 3.00 Virions were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SOS-PAGE) on 12.50/0 SOS-PAGE gels and stained with Coomassie brilliant blue G-250 according to established protocols (Sambrook and Russell, 2001). For serological analysis, proteins in replicate gels were transferred following electrophoresis to polyvinylidene difluoride membranes as described by Ullman et al. (1993). Commercially available IgG (Agdia Inc., Elkhart, IN, USA) for Tobacco mosaic virus (TMV) and related tobamoviruses [including Tomato mosaic virus (ToMV)] was used at a dilution of 1:200 (vol/vol) for detection of viral antigen. Goat anti-rabbit alkaline phosphatase conjugate (Bio-Rad) at a concentration of 1:3000 was used as the secondary antibody. Nitroblue tetrazolium and 5-bromo-4-chloro-3-indolyl phosphate substrates were used as recommended by the supplier (Bio-Rad). Double Antibody Sandwich, Enzyme-linked Immunosorbent (DAS-ELISA) OAS-ELISA tests of partially purified virus preparations, infected herbaceous plants and jasmine tissues (leaves, bark and flowers) were performed as described by Clark and Adams (1977). Commercial antibodies and conjugates specific for TMV and related tobamoviruses (Agdia Inc.) were used at 1:200 (vol/vol) dilutions as