During a survey of commercial pumpkin and squash fields for viruses, conducted in Illinois in 2005, Tobacco ringspot virus (TRSV) was identified for the first time in symptomatic pumpkin samples collected during August and September from Douglas, Kankakee, Piatt, and Tazewell counties in one of three, one of three, one of one, and one of seven samples tested, respectively. In an earlier study from southern Illinois, the only viruses detected in pumpkins were Cucumber mosaic virus, Papaya ringspot virus, Squash mosaic virus, Watermelon mosaic virus, and Zucchini yellow mosaic virus (2). TRSV has been reported in cucurbits from some states in the United States (1). We detected TRSV in symptomatic leaves exhibiting mild mosaic with leaf yellowing using a double-antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) kit (Agdia, Inc., Elkhart, IN). Samples were considered positive if the absorbance readings at 405 nm exceeded 3× the absorbance of the negative control. The presence of TRSV was confirmed by reverse transcription-polymerase chain reactions (RT-PCR). Total RNA was extracted from the symptomatic plants using TRIzol Reagent and reverse transcribed by M-MLV Reverse Transcriptase (Invitrogen, Carlsbad, CA). PCR was conducted using forward primer 5′-CTTGCGGCCCAAATCT ATAA-3′ and reverse primer 5′-ACTTGTGCCCAGGAGAGCTA-3′, which anneal to the conserved region in the coat protein gene. The reaction produced an amplification product of the expected size (348 bp). Hence, utilizing ELISA and RT-PCR tests, the presence of TRSV in pumpkin was determined, to our knowledge, for the first time in Illinois.
References: (1) R. Provvidenti. Tobacco ringspot. Page 42 in: Compendium of Cucurbit Diseases. T. A. Zitter et al., eds. The American Phytopathological Society, St. Paul, MN. 1996. (2) S. A. Walters et al. HortScience 38:65, 2003.
