Seed certification - post harvest control - Netherlands

Virus diseases
Samples for post-harvest control are taken during harvest. The apical eyes together with a part of the flesh are scooped from the collected tubers .
Dormancy is broken by immersing them for 10 minutes in a 1 ppm gibberellic acid solution.
Then the scoops are planted (10cmX10cm) under aphid free conditions (greenhouse).
After 4-5 weeks single stem potato plants will have grown.
The symptoms of any major viruses may become visible within a few weeks, but additional serological tests (ELISA) give clearer results.
Post harvest test: virus


Sample size and tolerance in post harvest test
Bacterial diseases
For brown rot the sample size is 250 tubers per 25 tonnes of seed potatoes. These tubers are first tested using the serological immunofluorescence (IF) test.
Samples are classified as suspect if they are found to contain fluorescent bacteria. The sample is then immediately subjected to the tomato-plant test.
Sap from the analyzed heel ends is injected in tomato plants. If the tomato plant becomes infected and brown rot bacteria can be isolated from the plants, the seed lot is declared infected with brown rot.
Brown rot IF-test
CRITICAL SAMPLE SIZE LABORATORY TESTS