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United States Department of Agriculture

Agricultural Research Service

Research Overview
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Accomplishments

·         Development of a standardized procedure for detection of eleven viruses and one viroid of potatoes.

·         Determined that the potato purple top phytoplasma is tuber-borne at a relatively high rate in major potato cultivars.

·         Demonstrated that various strains of Potato virus Y (PVY) are widespread in certified seed potatoes grown in the US and Canada.

·         Reported the occurrence of potato mop top virus (PMTV) for the first time in Washington State.

·         Potato zebra chip disease was found for the first time in Washington, Oregon, and Idaho in 2011.

 


Standardized virus detection method

Development of a standardized procedure for detection of eleven viruses and one viroid of potatoes.

 

The figure below shows the results of the reverse transcription polymerase chain reaction assay (RT-PCR) for alfalfa mosaic virus (AMV), potato virus Y (PVY), potato mop top virus (PMTV), and tobacco rattle virus (TRV) that was conducted under a standardized set of conditions.  The same conditions also successfully detect and identify tomato spotted wilt virus, impatiens necrotic spot virus, potato viruses A, M, S, and X, and potato spindle tuber viroid.  These standardized conditions make it easier to test for these important viruses of potato.


Purple top phyoplasma

Determined that the potato purple top phytoplasma is tuber-borne at a relatively high rate in major potato cultivars.

 

The potato purple top phytoplasma is an important pathogen of potatoes in the Columbia Basin of Washington and Oregon.  We found that the phytoplasma is transmitted to 4-96% of tubers and up to 50% of daughter plants from infected tubers.  Tuber-borne infections could result in a resurgence of purple top disease in this important potato growing region.

The figure below shows the symptoms in a Ranger Russet grown out from a phytoplasma-infected tuber.


Potato virus Y (PVY)

Demonstrated that various strains of Potato virus Y (PVY) are widespread in certified seed potatoes grown in the US and Canada.

Potato virus Y (PVY) is an important pathogen of potatoes and causes reductions in both yield and quality of the potato crop.  Over multiple years of testing, we found that various strains of PVY, including those that cause symptoms in tubers, are present in certified potato seed lots from diverse locations in the United States.  This evidence indicates that current procedures to reduce the level of PVY infection in seed crops need improvement.  The photo below shows the symptoms of a tuber necrotic strain (PVY-NTN) in a tuber of Russet Burbank, the most widely-grown variety of potatoes.


Potato mop top virus (PMTV)

Reported the occurrence of potato mop top virus (PMTV) for the first time in Washington State.

Prior to 2011, potato mop top virus (PMTV) had only been officially reported from the states of Maine and North Dakota.  Although it was believed that the virus was indeed in Washington State, this was not confirmed until samples collected from the Columbia Basin of Washington tested positive for the virus.  The photograph below shows the brown arcs typical of PMTV in a Washington grown potato.  This virus is transmitted by a soil-inhabiting fungus and is particularly difficult to control.


Potato zebra chip disease

Potato zebra chip disease was found for the first time in Washington, Oregon, and Idaho in 2011.

 

Prior to 2011, the zebra chip disease (ZC) was only reported from the central United States, Mexico, Central America, and New Zealand.  In the summer of 2011 this serious disease was first found in potatoes grown in Oregon, Washington, and Idaho, and caused millions of dollars in losses.  Together, these three states produce more than half of the US potatoes.  ZC disease is caused by a bacterium that is transmitted to potatoes by a small insect, the potato psyllid.  Our work has informed the potato industry in the Pacific Northwest of the presence of this important disease.  We are continuing to study this disease and the biology of the psyllid in efforts to reduce the impact of ZC on the potato industry in the future.  The photo below shows the severe tuber discoloration typical of ZC in a potato grown in Washington in 2011.

 


Last Modified: 3/13/2012