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2006. Plant Management Network. This article is in the public domain.
Accepted for publication 8 May 2006. Published 7 June 2006.


First Report of Tomato spotted wilt virus in Tomatillo in Florida


Scott Adkins, USDA-ARS-USHRL, Fort Pierce, FL 34945; M. Timur Momol and Hank Dankers, North Florida Research and Education Center, University of Florida, IFAS, Quincy 32351; Stuart Reitz, USDA-ARS-CMAVE, Tallahassee, FL 32308; and Stephen Olson, North Florida Research and Education Center, University of Florida, IFAS, Quincy 32351


Corresponding author: Scott Adkins.  SAdkins@ushrl.ars.usda.gov


Adkins, S., Momol, M. T., Dankers, H., Reitz, S., and Olson, S. 2006. First report of Tomato spotted wilt virus in tomatillo in Florida. Online. Plant Health Progress doi:10.1094/PHP-2006-0607-03-BR.


Tomatillo (Physalis ixocarpa), a member of the Solanaceae, has cultural requirements similar to those of tomato and produces an edible, tomato-like fruit that is encased in a papery husk (Fig. 1C). The fruit is frequently used to make relishes and sauces.

In the spring of 2004 and 2005, symptoms similar to those induced by the thrips-vectored Tomato spotted wilt virus (TSWV) were observed on tomatillo in cultivated fields in Gadsden county and experimental plots in Leon county, both in northern Florida. Symptoms included chlorosis and stunting of young leaves and distinct chlorotic rings and ring patterns on older leaves (Fig. 1). The incidence of symptomatic plants ranged from 5 to 10% in both counties in both years.


       
 

Fig. 1. Symptoms of Tomato spotted wilt virus on tomatillo. Young leaves show chlorosis and stunting (A), whereas older leaves show distinct chlorotic rings and ring patterns (B). An uninfected tomatillo plant with fruit, leaf and flower is shown for comparison (C).

 

The morphology of cytoplasmic inclusion bodies found in all plants assayed indicated the presence of a tospovirus. Commercially available serological reagents [Immunostrip or double antibody sandwich-enzyme linked immunosorbent assay (DAS-ELISA); Agdia, Elkhart, IN] specifically identified TSWV in symptomatic but not symptomless tomatillo plants.

Reverse transcription-polymerase chain reaction (RT-PCR) using primer pair gL3637 and gL4510 (2) and primer pair TSWV723 and TSWV722 (1) amplified fragments of the expected size (938 and 620 base pairs, respectively) only from total RNA extracted from symptomatic plants (Fig. 2) [using an RNeasy Plant Mini Kit (Qiagen, Valencia, CA) following the manufacturer’s instructions]. Nucleotide and deduced amino acid sequences of a 579 base pair region of the nucleocapsid (N) protein gene from the TSWV723/TSWV722 RT-PCR product were 95 to 99% and 95 to 100% identical, respectively, to all TSWV N-gene sequences in GenBank. No product was amplified from total RNA extracted from symptomless plants.


   
 

Fig. 2. Detection of Tomato spotted wilt virus (TSWV) infection in tomatillo plants by reverse transcription-polymerase chain reaction (RT-PCR). Total RNA was extracted from leaves of non-symptomatic (NS; lane 1) and symptomatic (S; lanes 2 and 3) tomatillo, amplified by RT-PCR with tospovirus primers (gL3637 and gL4510, lanes 1 and 2; TSWV723 and TSWV722, lane 3), analyzed by native electrophoresis on a 2% agarose gel and stained with ethidium bromide. Lane 4 (M) contains markers with sizes in kilobases (kb) indicated to the right of the gel.

 

During 2004 and 2005, thrips species observed on tomatillo included western flower thrips (Frankliniella occidentalis [Pergande]) and Florida flower thrips (F. bispinosa [Morgan]). Both species are known vectors of TSWV (4) suggesting one or both as a likely means of tomatillo infection by TSWV.

To the best of our knowledge this is the first report of TSWV on tomatillo in Florida, although TSWV was observed in this plant in Georgia six years ago (3). TSWV continues to expand its geographic and host ranges and remains an economically important disease constraint for the production of vegetable, agronomic and ornamental crops in the southeastern United States.


Literature Cited

1. Adkins, S., and Rosskopf, E. N. 2002. Key West nightshade, a new experimental host for plant viruses. Plant Dis. 86:1310-1314.

2. Chu, F.-H., Chao, C.-H., Chung, M.-H., Chen, C.-C., and Yeh, S.-D. 2001. Completion of the genome sequence of Watermelon silver mottle virus and utilization of degenerate primers for detecting tospoviruses in five serogroups. Phytopathology 91:361-368.

3. Díaz-Pérez, J. C., and Pappu, H. R. 2000. First report of Tomato spotted wilt virus infection of tomatillo in Georgia. Plant Dis. 84:1155.

4. Whitfield, A. E., German, T. L, and Ullman, D. E. 2005. Tospovirus-thrips interactions. Annu. Rev. Phytopath. 43:459-489.