Impatiens necrotic spot virus (INSV; genus Tospovirus) was detected in experimental greenhouse-grown potatoes (Solanum tuberosum) and Nicotiana benthamiana in New York State in July and August of 2003 and 2004. Potato leaves exhibiting necrotic lesions with a concentric pattern similar to those induced by Tomato spotted wilt virus (1) were observed on cvs. Atlantic, Huckleberry, NY115, and Pentland Ivory. The presence of INSV was confirmed using double-antibody sandwich enzyme-linked immunosorbent assay and a rapid ‘ImmunoStrip’ assay (Agdia, Inc., Elkhart, IN). INSV-specific sequences were amplified from total RNA extracts using reverse transcription-polymerase chain reaction with ‘Tospovirus Group’ primers (Agdia, Inc.) and two independently amplified DNAs were sequenced. A common sequence of 355 nucleotides (GenBank Accession No. AY775324) showed 98% identity to coding sequences in an INSV L RNA. The virus was mechanically transmitted to potato and N. benthamiana and could be detected in asymptomatic, systemically infected potato leaves. Stems nodes and leaves were removed from infected potato plants, and sterile in vitro plantlets were established (2). None of the regenerated in vitro plantlets of cvs. Pentland Ivory (6 plantlets) or NY115 (5 plantlets) were infected with INSV. Two of ten regenerated cv. Atlantic plantlets initially tested positive, but INSV could not be detected after 6 months in tissue culture. In vitro tissue culture plantlets could not be established from infected cv. Huckleberry plants, even though they were consistently obtained from uninfected plants. Infected greenhouse plants were grown to maturity and the tubers harvested, stored for 6 months at 4°C, and replanted in the greenhouse. INSV could not be detected in plants from 26 cv. Huckleberry, 4 cv. NY115, or 4 cv. Atlantic tubers. Although this isolate of INSV was able to systemically infect potato, it was not efficiently maintained or transmitted to progeny tubers. This might explain why INSV has not been reported as a problem in potato production. Lastly, in both years, dying N. benthamiana provided the first sign of a widespread greenhouse infestation of INSV in a university facility housing ornamental and crop plants. INSV induced a systemic necrosis in N. benthamiana, and this host may be useful as a sensitive ‘trap’ plant indicator for natural infections in greenhouse production.
References: (1) T. L. German. Tomato spotted wilt virus. Pages 72--73 in: Compendium of Potato Diseases. W. R. Stevenson et al., eds. The American Phytopathological Society, St. Paul, 2001. (2) S. A. Slack and L. A. Tufford. Meristem culture for virus elimination. Pages 117--128 in: Fundamental Methods of Plant Cell, Tissue and Organ Culture and Laboratory Operations. O. L. Gamborg and G. C. Philips, eds. Springer-Velag, Berlin, 1995.
