March 12, 2005
Source: American Phytopathological Society, Plant Disease Notes [edited]

Impatiens necrotic spot virus in greenhouse-grown potatoes in New York State
K. L. Perry, L. Miller, and L. Williams, Department of Plant Pathology, 334 Plant Science Bldg. Cornell University, Ithaca, NY 14853. Plant Dis. 89:340, 2005; published on-line as DOI: 10.1094/PD-89-0340C. Accepted for publication 9 Dec 2004.

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 2 independently amplified DNAs were sequenced. A
common sequence of 355 nucleotides (GenBank Accession No. AY775324) showed 98 percent 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. 2 of 10 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 deg 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 1st 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 OrganCulture and Laboratory Operations. O. L. Gamborg and G. C. Philips, eds. Springer-Verlag, Berlin, 1995.

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[This disease is a conundrum, of sorts because it involves production of potato in an experimental glasshouse rather than a production field. Under the growing conditions prevailing in the glasshouse, the virus failed to
replicate sufficiently to maintain the virus in infected potato. The interesting aspect of this disease is that INSV-infected _N. benthiamiana_ is an effective indicator of the disease. Disease management would require applications of insecticides to reduce populations of the insect (_Frankliniella occidentalis_). Other thrips have not been identified as vectors, but that may have changed. The biology of INSV is similar to that of TWSV, such that the 2 viruses are often recorded together.

Links: <http://www.umass.edu/umext/floriculture/fact_sheets/pest_management/insvtswv.html>
<http://www.ces.ncsu.edu/depts/ent/notes/O&T/production/note120.html>
<http://www.apsnet.org/online/feature/tospovirus/>
<http://www.eppo.org/QUARANTINE/virus/Impatiens_necrotic_spot_virus/INSV00_map.htm>
- Mod.DH]