PROJECT OVERVIEW

PCR‑Based Diagnostics for Seed Potato Post Harvest Virus Testing

Markus Schmülgen

Food Development Centre

Manitoba Agriculture and Food

(204) 239-3436

ARDI Project:

Total Approved:

Date Approved:

#01-488

$6,500

August 17, 2001

Seed potatoes routinely undergo post harvest testing for potato virus Y (PVY) and potato leaf roll virus (PLRV).  Both diseases are regulated by the Canadian Food Inspection Agency (CFIA) and are indicators of seed health and quality.  Traditionally, post-harvest testing is done by ELISA techniques or by winter grow out tests in California.  However, there are advantages and drawbacks to each of these methods.  ELISA testing requires leaves for analysis so tubers must be grown out in a greenhouse to obtain sample material.  Winter grow out tests provide the opportunity to view disease symptoms, but accurate readings are often difficult to obtain because of the influence of nutritional and environmental factors.  Because of this, the seed potato industry in Manitoba expressed an interest in exploring new diagnostic technology.  Polymerase chain reaction (PCR) is a DNA/RNA based diagnostic technology that has added a new dimension to disease diagnosis.  PCR-based techniques can be used to test tuber, leaf and aphid samples.  No other method has this range of sample versatility.  Since PCR-based tests can be performed using dormant tuber tissue, results can be obtained more timely compared to methods that require sprouting of tubers, but it is still unclear as to how PCR-based virus diagnostics compare to the standard ELISA and winter grow out tests.

The objective of this project is to compare PCR-based potato virus testing with the current industry standards of ELISA and winter grow out testing.  This project will be initiated by collecting 3 seed lots, one each from 3 seed potato growers.  Each grower will collect a representative sample consisting of approximately 2000 tubers.  From this sample, subsamples will be collected for ELISA testing (400 tubers), winter grow out testing (400 tubers) and PCR testing (200 tubers).  The ELISA samples will be sent to Phyto Diagnostics Laboratory in British Columbia, the winter grow out samples will be sent to Hawaii and/or California, and the PCR samples will be sent to the Food Development Center (FDC).  The FDC will slice and juice both ends of each tuber.  In addition, composite samples of 10 tubers will be made from the individual tuber juice extracts.  In total, 50 individual tuber samples and 5 composites of 10 from the same tubers will be processed and analyzed each week.  Juice samples will be sent to the Veterinary Services Laboratory (VSL) immediately after extracting.  The VSL will extract RNA from the juice sample and perform a PCR test using techniques developed by Dr. Rudra Singh, Agriculture and Agri-Food Canada, Fredericton, in order to determine virus levels.  Following testing, results will be compiled and analyzed, and recommendations will be issued for the future use of a PCR-based diagnostic service for potato virus testing.

Funding for this project has been provided in part by the Seed Potato Growers Association of Manitoba, Midwest Food Products, Keystone Vegetable Producers Association, and J.R. Simplot.

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