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Over lOU years after its discovery, Tobacco mosaic virus (TMV) remains an economically important pathogen for producers of many vegetatively propagated crops including petunias (Petunia x hybrida). To directly address this concern, we have developed a robust system to determine efficacy of disinfectants for treating TM V-contaminated cutting tools using a combination of preliminary screens and replicated trials. Contrary to widely held beliefs, wild-type (wt) TMV and four additional tobamovirus species infected four petunia cultivars without producing obvious viral symptoms. In contrast, a petunia isolate of TMV with 99.0% (nucleotide) and 99.4% (amino acid) coat protein sequence identity to wt TMV produced symptoms on all but one tested cultivar. We also show that TMV transmission can occur up to the twentieth petunia plant cut following a single cutting event on a TM V-infected plant. Although many new products are now available, treatment of TMV-contaminated tools with a 20% (wt/vol) solution of nonfat dry milk (NFDM) plus 0.1% Tween 20 or a 1:10 dilution of household bleach (0.6% sodium hypochlorite), two "old standbys", completely eliminated TMV transmission to petunias. Treatment of contaminated tools with 1% (wt/vol) Virkon S or 20% NFDM also significantly reduced the incidence of infected petunias. Other treatments identified in the preliminary screens are candidates for the second phase of screening that simulates contamination during the process of taking cuttings. [ABSTRACT FROM AUTHOR]

Hosta virus X (HVX) is rapidly becoming a serious pathogen of commercially important hosta plants worldwide. We report here biological and molecular characterization of a U.S. isolate of HVX, HVX-37. HVX-37 infectivity was tested in 21 hosta cultivars over three growth seasons, and three types of responses were defined based upon the ability of the virus to cause local and/or systemic infections. Four cultivars resistant to systemic HVX infection were identified. The full-length sequence of the HVX-37 genome was determined, the first complete sequence of a U.S. HVX isolate. Comparison with the previously sequenced HVX-Korea (Kr) genome revealed a high level of sequence similarity, as well as some differences. Notably, a 105-nucleotide long, near-perfect direct repeat in the Kr isolate is absent in HVX-37. The accuracy of the HVX-37 genome sequence was confirmed by infectivity of in vitro transcripts synthesized from a full-length HVX-37 cDNA on Nicotiana benthamiana and hosta plants. [ABSTRACT FROM AUTHOR]

Foliar symptoms suggestive of virus infection were recently observed on the noxious weed tropical soda apple (Solanum viarum) in Florida. An agent was mechanically transmitted to Nicotiana benthamiana, and virions were isolated from systemically infected leaves. Rod-shaped particles ~300 nm in length were observed in the partially purified preparations by electron microscopy. The host range determined by mechanical inoculation with purified virions included all tested plants in the Solanaceae (16 species including the important vegetable crops, pepper and tomato) and Chenopodiaceae (2 species) but excluded all tested plants in the Amaranthaceae, Apocynaceae, Brassicaceae, Caryophyllaceae, Cucurbitaceae, Fabaceae, Lamiaceae, Malvaceae, and Tropaeolaceae, including several common virus indicator hosts. Comparisons of the coat and movement protein nucleotide and deduced amino acid sequences of this putative tobamovirus with recognized members of this genus, indicate that it is a novel tobamovirus that shares the highest level of sequence identity with Pepper mild mottle virus followed by other members of the Solanaceae-infecting subgroup of tobamoviruses. The virus, for which the name Tropical soda apple mosaic virus (TSAMV) is proposed, was found to be widespread in tropical soda apple in peninsular Florida during an initial survey. TSAMV contamination of seed from infected tropical soda apple plants was found, suggesting that seed transmission may be important for TSAMV dissemination and epidemiology. [ABSTRACT FROM AUTHOR]

Tobamoviruses are among the best characterized and most studied plant viruses. Three subgroups of tobamoviruses correspond to viral genome sequence and host range to include those viruses infecting (i) solanaceous plants, (ii) brassicas, or (iii) cucurbits or legumes. We isolated a virus from Florida landscape plantings of the malvaceous plant hibiscus (Hibiscus rosasinensis) that appears to be a tobamovirus based upon its virion morphology, genome organization, and coat protein sequence. The experimental host range of this virus included five malvaceous species but excluded all tested brassica, cucurbit, and legume species and 12 of the 19 solanaceous species tested. The unique host range and comparison of coat protein gene and protein sequences with those of recognized tobamoviruses indicate that this is a novel tobamovirus. A limited survey revealed that this virus is widespread in hibiscus and related species in the Florida landscape. [ABSTRACT FROM AUTHOR]