Tospoviruses (Family Bunyaviridae, Genus Tospovirus)

Viruses in the genus Tospovirus cause significant worldwide crop losses. The genus name is derived from the name of its first member, Tomato spotted wilt virus (TSWV). Initially observed in Australia in 1915, the spotted wilt disease of tomato was later shown to be of viral origin. The causal agent was designated TSWV, and considered to be the sole member of the tomato spotted wilt group of plant viruses until the early 1990s. At this time, the identification and characterization of several similar viruses, including Impatiens necrotic spot virus (INSV), led to the creation of the plant-infecting Tospovirus genus within the Bunyaviridae family, a large group of predominantly animal-infecting viruses. More than a dozen tospoviruses have since been identified and characterized and previously unknown species of the genus continue to be described on a regular basis. Three tospoviruses, TSWV, INSV and Iris yellow spot virus (IYSV), are known to occur in the US. This document is Fact Sheet PP-212, one of a series of the Plant Pathology Department, Florida Cooperative Extension Services, Institute of Food and Agricultural Sciences, University of Florida. Published October 2005.

THE MOST COMMON DISEASES OF ORNAMENTAL PLANTS IN THE ENTITY OF REPUBLIC OF SRPSKA (BOSNIA AND HERZEGOVINA)

During five year period (2011-2015) on territory of Republic of Srpska thecontinuous monitoring was carried out on different ornamental flowers for thepresence of plant diseases. For laboratory analysis following species Alyssum sp.,Aster sp., Bacopa sp., Begonia sp., Bellis perennis, Calceolaria sp.,Chrysanthemum sp., Cyclamen sp., Dahlia sp., Dianthus sp., Fuchsia sp., Gazaniasp., Gloxinia sp., Lobelia sp., Myosotis sp., Pelargonium sp., Petunia sp.,Petuniaxhybrida, Phlox sp., Plectranthus sp., Portulaca grandiflora, Primula sp.,Ranunculus sp., Rusmarinus officinalis, Salvia sp., Sansevaria sp., Tagetes sp.,Impatiens sp., Verbena sp. and Viola sp. were taken. Determination of causalpathogens was carried out on the basis of studying their morphological, pathogenic,biochemical and physiological, serological and molecular characteristics. The mostcommon causal pathogens were Alternaria sp., Botrytis sp., Golvonomyces sp.,Pestalotia sp., Phomopsis sp., Peronospora sp., Phytophtora sp., Puccinia sp. andSeptoria sp. Also, in much less extent, bacterial and viruses diseases were present.The most common bacterial diseases appear to be genera Pseudomonas andErwinia, while the most frequent plant viruses were Tomato spotted wilt virus(TSWV) and Impatiens necrotic spot virus (INSV).

Variation within Lactuca spp. for Resistance to Impatiens necrotic spot virus

Lettuce (Lactuca sativa L.) production in coastal California, one of the major lettuce-producing areas of the United States, is regularly affected by outbreaks of Impatiens necrotic spot virus (INSV), a member of the genus Orthotospovirus. Transmission of INSV among lettuce crops in this growing region has been attributed predominantly to the western flower thrips (Frankliniella occidentalis). INSV is acquired by first- or second-instar thrips nymphs feeding on infected host plants (not necessarily lettuce). The virus replicates within the insect vector, and is transmitted to new plants by adult thrips as they feed on epidermal and mesophyll cells of susceptible host plants. All currently grown cultivars of lettuce are susceptible to the disease. Screening lettuce for resistance to INSV under field conditions is problematic because natural infections appear sporadically and the virus is not evenly distributed across infected fields. We have developed a greenhouse-based assay that uses viruliferous thrips in combination with mechanical inoculation that allows dependable, year-round screening for resistance. In all, 89 cultivars, breeding lines, and plant introductions of cultivated lettuce, together with 53 accessions from 11 other Lactuca spp., 4 accessions from two dandelion (Taraxacum) species, and 4 tomato (Solanum lycopersicum L.) lines were evaluated for resistance to INSV. All tested material was susceptible to INSV to varying degrees, with the exception of two tomato lines that carry the Sw-5 gene that confers resistance to Tomato spotted wilt virus, a virus closely related to INSV. In cultivated lettuce, a partial resistance to INSV was observed in cultivars Amazona, Ancora, Antigua, Commodore, Eruption, Iceberg, La Brillante, Merlot, Telluride, and Tinto. Limited comparison of the greenhouse-based screening results with the data from opportunistic evaluations of resistance on 775 lettuce accessions from six field trials indicates consistency of results from both greenhouse and field environments. The most resistant lettuce accessions are being incorporated into our breeding program for introgression of resistance into lettuce breeding lines.

Development of Reverse Transcription Thermostable Helicase-Dependent DNA Amplification for the Detection of Tomato Spotted Wilt Virus

A protocol for the reverse transcription-helicase-dependent amplification (RT–HDA) of isothermal DNA was developed for the detection of tomato spotted wilt virus (TSWV). Specific primers, which were based on the highly conserved region of the N gene sequence in TSWV, were used for the amplification of virus's RNA. The LOD of RT–HDA, reverse transcriptase-loop-mediated isothermal amplification (RT-LAMP), and reverse transcriptase-polymerase chain reaction (RT-PCR) assays were conducted using 10-fold serial dilution of RNA eluates. TSWV sensitivity in RT–HDA and RT-LAMP was 4 pg RNA compared with 40 pg RNA in RT-PCR. The specificity of RT–HDA for TSWV was high, showing no cross-reactivity with other tomato and Tospovirus viruses including cucumber mosaic virus (CMV), tomato black ring virus (TBRV), tomato mosaic virus (ToMV), or impatiens necrotic spot virus (INSV). The RT–HDA method is effective for the detection of TSWV in plant samples and is a potential tool for early and rapid detection of TSWV.