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Title: First report of Impatiens necrotic spot virus infecting greenhouse-grown potatoes in Washington State

Author
item Crosslin, James
item HAMLIN, LAUNA - Washington State University

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/4/2010
Publication Date: 11/15/2010
Citation: Crosslin, J., Hamlin, L. 2010. First report of Impatiens necrotic spot virus infecting greenhouse-grown potatoes in Washington State. Plant Disease. 94:1507.

Interpretive Summary: Impatiens necrotic spot virus (INSV) is an emerging pathogen of many crops. This virus is transmitted by thrips as is a major problem in greenhouse grown plants. This paper makes the first report of INSV infecting greenhouse potatoes in Washington State.

Technical Abstract: In April and May 2010, potato (Solanum tuberosum L. cv. Atlantic) plants grown from pre-nuclear minitubers in three separate greenhouses located at the USDA-ARS facility in Prosser, WA exhibited necrotic spots on leaves similar to those produced by the early blight pathogen, Alternaria solani (Sor.). Fungicide sprays did not reduce incidence of the symptoms. Observations suggested the symptoms were associated with thrips feeding damage so plants were tested for Tomato spotted wilt virus (TSWV) and Impatiens necrotic spot virus (INSV) with Immunosticks® from Agdia, Inc. Symptomatic tissues were positive for INSV in these tests and negative for TSWV. Subsequent reverse transcription polymerase chain reaction (RT-PCR) tests with INSV specific primers (4) were also positive for INSV. The 906 bp amplicon was cloned and three clones were sequenced. BLAST analysis of the consensus sequence (GenBank accession HM802206) showed 99% identity to INSV accessions D00914 and X66972, and 98% identity to numerous other INSV isolates. The isolate, designated INSV pot 1, was mechanically inoculated to potato cv. GemStar and produced local, spreading necrotic lesions but did not go systemic, as determined by RT-PCR tests of upper leaves thirty days after inoculation. The local necrotic lesions on GemStar tested positive for INSV by Immunostick and RT-PCR. The original source of the INSV inoculum is unknown. However, hairy nightshade (Solanum sarrachoides Sendtn.) and plantain (Plantago major L.) weeds in an ornamental planting near one of the affected greenhouses tested positive for INSV by Immunostick. The nightshade showed no obvious virus symptoms but the plantain showed distinct necrotic rings. Subsequently, INSV infected potato plants of cv. Desiree were found in another greenhouse near the initial site. In addition to the necrotic lesions on leaves, these potato plants also showed necrosis of petioles and stems. INSV is transmitted by a number of species of thrips, but the western flower thrips is considered the most important under greenhouse conditions. Both INSV and the thrips vector have large host ranges including many crops and weeds, and have become increasingly important in recent years (1, 3). INSV was reported on greenhouse-grown potatoes in New York in 2005 (2).