ARS | Publication request: Detection of potato mop top virus (Furovirus) on potato in southeast Idaho

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 6, 2012
Publication Date: N/A

Interpretive Summary: Potato mop top virus (PMTV) can cause internal necrosis in potato tubers resulting in brown arcs and streaks in the potato. PMTV was first reported from the 2001 crop in Maine and in Canada from samples from the U.S. and Canada that were tested during 2001-2002. More recently, positive PMTV samples have been reported in North Dakota and Washington. Samples of Modoc, a red variety, grown in eastern Idaho were observed with internal necrotic arcs. Tests were done for PMTV and for tobacco rattle virus (TRV) which can cause a similar symptom. Two types of testing were done, a molecular based RT-PCR and a serological ELISA test. The RT-PCR test was done for PMTV and TRV and the ELISA was done for PMTV. All tests were postive for PMTV and negative for TRV. DNA sequence analysis of the postive test (called RT-PCR) was compared with other PMTV sequences recorded in GenBank and were identical to sequences from North Dakota, U.S.A. and Finland, and nearly identical to a sequence from Washington, U.S.A. These results confirm that PMTV exists in Idaho, which produces nearly a third of the fall grown potatoes in the U.S. in 2011. This positive PMTV report alerts growers and processors to this disease which can cause quality defects and is difficult to control.

Technical Abstract: In February 2012, commercially produced potato (Solanum tuberosum) tubers, cv. Modoc, grown in eastern Idaho were observed with internal necrotic arcs and lines. Samples were obtained from potatoes that had been washed and packed. No external symptoms were evident. The incidence of symptomatic tubers ranged from 2-3%. Initially two tubers were tested by RT-PCR at Aberdeen, Idaho; one with symptoms and one without, with primers specific for Tobacco rattle virus (TRV) (4) and Potato mop top virus (PMTV) (1). RT-PCR results showed that the symptomatic tuber produced a band at 416 bp with the PMTV primers, consistent with a PMTV-positive control. No amplification was observed with the TRV primers. The asymptomatic tuber was negative for both PMTV and TRV. Subsequently, four additional symptomatic tubers from the same lot were tested at USDA-ARS in Prosser, WA by RT-PCR with primers for PMTV (2) and TRV (4). Samples were tested alongside two PMTV-positive controls from cv. Alturas tubers (1), a healthy cv. Russet Burbank control, and a water control. Results showed that amplified products of 460 bp were obtained with the PMTV primers for the four symptomatic tubers and the four tubers were negative for TRV. In addition, symptomatic tissue from the four tubers tested positive for PMTV by enzyme linked immunosorbent assay (ELISA) using a commercially available kit (Adgen, Ayr, Scotland). Symptomless Russet Burbank tubers and water controls were negative in RT-PCR and ELISA tests. The 460 bp PMTV amplicon from two symptomatic Modoc tubers were cloned and sequenced. The sequences were identical and the sequence (GenBank accession JX239990) was 100% identical to the corresponding sequences of PMTV isolates from North Dakota (HM776172) and Finland (AM503632). There was one nucleotide difference from the corresponding sequence of a PMTV isolate from Washington (JN132117). These tests confirm that PMTV exists in eastern Idaho and follows reports of PMTV in commercial potatoes in Washington (1), North Dakota (2), and in commercial potatoes and at the Aroostook Research Farm in Maine (3). In 2011, 129,000 ha of potatoes were grown in Idaho, representing 29% of the fall grown potatoes in the United States The confirmation of PMTV alerts growers and processors to the presence of this virus in this important potato-producing state.