Impatiens necrotic spot virus and Tomato spotted wilt virus Diagnosed in Phalaenopsis Orchids from Two Florida Nurseries.

In October 2006 (Arcadia, FL) and January 2007 (Sorrento, FL), several white Phalaenopsis orchids with large chlorotic/necrotic ringspot symptoms were sent to the Division of Plant Industry, Gainesville, FL. Symptomatic leaf tissues were tested with the Agdia immunostick-comb (Agdia, Elkhart, IN) for Impatiens necrotic spot virus (INSV), Tomato spotted wilt virus (TSWV), Cucumber mosaic, and Tobacco mosaic virus. Plants from the nursery in Sorrento, FL tested positive for TSWV, while those from the nursery in Arcadia, FL tested positive for INSV. Symptomless leaves from the infected plants tested negative for the viruses with the immunostick-comb. The plants also were tested for TSWV and INSV by double-antibody (DAS)-ELISA (Agdia Inc.) with the same results. Total RNA was extracted from one symptomatic orchid leaf from each nursery. Reverse transcription (RT)-PCR was performed with the universal tospovirus primer set BR60and BR65 (1). PCR bands of the expected size were amplified from each leaf. PCR products were sequenced directly. The orchid leaf that tested positive for TSWV by ELISA produced a 495-bp sequence with 97% identity to several isolates of the TSWV nucleocapsid protein gene listed in GenBank (Accession Nos. AY744479, AY8770391, DQ376185, and AF02659). The orchid leaf that tested positive for INSV by ELISA produced a 396-bp sequence with 98 to 99% identity to several isolates of the INSV nucleocapsid protein gene (Accession Nos. D00914, DQ425096, X66972, and AD109100). Although these viruses have been reported a few times in orchids previously (2,3), to our knowledge, this is the first time they have been reported in this host in Florida. In addition, white Phalaenopsis spp. appears to be a local lesion host and not a systemic host for these viruses. References: (1) M. Eiras et al. Fitopatol. Bras. 26:170, 2001. (2) J. S. Hu et al. Plant Dis. 77:464, 1993. (3) S. T. Koike and D. E. Mayhew. Orchids 70:746, 2001.