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First Report of Pepper mottle virus Infecting Tomato in Hawaii

In August 2011, tomato (Solanum lycopersicum L.) fruit from a University of Hawaii field trial displayed mottling symptoms similar to that caused by Tomato spotted wilt virus (TSWV) or other tospoviruses. The foliage from affected plants, however, appeared symptomless. Fruit and leaf tissue from affected plants were negative for TSWV analyzed by double antibody sandwich (DAS)-ELISA and/or TSWV ImmunoStrips (Agdia, Elkhart, IN) when performed following the manufacturer's instructions. Total RNA from a symptomatic and an asymptomatic plant was isolated using an RNeasy Plant Mini Kit (Qiagen, Valencia, CA) and reverse transcribed using Invitrogen SuperScript III reverse transcriptase (Life Technologies, Grand Island, NY) and primer 900 (5′- CACTCCCTATTATCCAGG(T)₁₆-3′) following the enzyme manufacturer's instructions. The cDNA was then used as template in a universal potyvirus PCR assay using primers 900 and Sprimer, which amplify sequences encoding the partial inclusion body protein (NIb), coat protein, and 3′ untranslated region of potyviruses (1). A ~1,700-bp product was amplified from the cDNA of the symptomatic plant but not the asymptomatic plant. This product was cloned using pGEM-T Easy (Promega, Madison, WI) and three clones were sequenced at the University of Hawaii's Advanced Studies in Genomics, Proteomics, and Bioinformatics laboratory. The 1,747-bp consensus sequence of the three clones was deposited in GenBank (Accession No. JQ429788) and, following primer sequence trimming, found to be 97% identical to positions 7,934 through 9,640 of Pepper mottle virus (PepMoV; family Potyviridae, genus Potyvirus) accessions from Korea (isolate ‘217’ from tomato; EU586126) and California (isolate ‘C’ from pepper; M96425). To determine the incidence of PepMoV in the field trial, all 292 plants representing 14 tomato cultivars were assayed for the virus 17 weeks after planting using a PepMoV-specific DAS-ELISA (Agdia) following the manufacturer's directions. Plants were considered positive if their mean absorbance at 405 nm was greater than the mean absorbance + 3 standard deviations + 10% of the negative control samples. The virus incidence ranged from 4.8 to 47.6% for the different varieties, with an overall incidence of 19.9%. Although plant growth was not noticeably impaired by PepMoV infection, the majority of fruit from infected plants was unsaleable, making PepMoV a considerable threat to tomato production in Hawaii. PepMoV has been reported to naturally infect tomato in Guatemala (3) and South Korea (2). To our knowledge, this is the first report of this virus in Hawaii and the first report of this virus naturally infecting tomato in the United States.

References: (1) J. Chen et al. Arch. Virol. 146:757, 2001. (2) M.-K. Kim et al. Plant Pathol. J. 24:152, 2008. (3) J. Th. J. Verhoeven et al. Plant Dis. 86:186, 2002.