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First report of Tomato chlorotic dwarf viroid and Southern tomato virus infecting greenhouse tomato in Hawaii.

Alejandro Olmedo-Velarde: University of Hawaii at Manoa, Department of Plant and Environmental Protection Sciences

<div>In January 2017, greenhouse tomato [<em>Solanum lycopersicum</em> (L.)] plants showing stunting and foliar yellowing, reddening, interveinal chlorosis, and epinasty, were reported from the Island of Hawaii, Hawaii, USA. Initial shotgun cloning and sequencing using double stranded (ds)-RNA extracted from symptomatic plants revealed <em>Southern tomato virus</em> (STV, genus <em>Amalgavirus</em>) was present and a potential causal agent of the disease. Screening of 14 symptomatic and 8 asymptomatic plants by STV-specific reverse transcription (RT)-PCR indicated STV was not clearly associated with the observed symptoms. Symptomatic samples were subsequently subjected to universal <em>Pospiviroid</em> RT-PCR and produced the expected 198 bp amplification product. Cloning and sequencing revealed the product was 99% identical to <em>Tomato chlorotic dwarf viroid </em>(TCDVd) isolate ‘GBVdC_TCDVd04’ (GenBank Accession KU714934). A TCDVd-specific RT-PCR assay was developed. This assay, combined with sequencing of amplification products, was used to confirm the identity of the viroid in the symptomatic samples. However, TCDVd was found in asymptomatic tomato samples with this assay, suggesting it may not be the causal agent of the symptoms in tomato. Further investigation is needed to understand the role of STV and TCDVd in the symptomatic and asymptomatic tomatoes, as well as the presence and genetic diversity of this viroid in commercial tomato seeds.</div>