Frequently Asked Questions (FAQ) Laboratory testing

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You can find more information about our accreditations on our website.

You can register for our newsletters on our website.

The laboratory has three different certifications/accreditations:

• NEN-EN-ISO 9001:2015
• NEN-EN-ISO/IEC 17025:2017
• ISTA Accreditation

For agricultural crops, please contact our fellow inspection service NAK in Emmeloord.

You can find this in the Price list Laboratories 2024 on our website behind the relevant button.

You will find our current portfolio in the Price list Laboratories 2024. For vegetable crops, which tests we can perform is stated per crop. For plant material, a separate chapter lists which tests are available.

Do you have any questions?
Please contact the Support team of the laboratory

All our tests have been validated on in-vivo material. Depending on the testing technique used, in-vitro material can also be tested. The PCR technique is very sensitive and can generally be used. The ELISA technique is less robust and is not recommended. Preferably have the propagating material tested. Alternatively, again later when the plants have been in the greenhouse for a few weeks.

Virus testing requires young, fully-grown leaves.

You can find this in the Price list Laboratories 2024 on our website under the desired test.

• Take samples from a place where the new symptoms are visible. Running laboratory tests on dead plants is not always possible.
• Take a sample before any crop protection products are applied. Crop protection products can destroy or mask the symptoms caused by pathogens and interfere with the laboratory tests
• If the symptoms are unclear, submit the entire plant.
• If symptoms are unclear or if the plants are uncommon, submit part of a healthy specimen. Pack the healthy sample separately. Indicate that it is healthy material on the label.
• Prevent leaves and flowers being contaminated by soil or substrate sent with the sample. Place a separate plastic bag around the roots and seal with an elastic band around the stem.
• Pack the entire sample in paper to prevent dehydration and rotting. Paper will regulate the moisture content in the plastic bag.

For export, an inspector often arranges the sampling. You can send an email to planning@naktuinbouw.nl. They can tell you exactly what you need to do.

• Disinfected seeds carry residues to a greater or lesser extent. The most obvious example is seeds coated with crop protection agents. The aim is to remove as much fungi and / or bacteria from the seeds as possible. These products may potentially influence the tests.
• Treated (disinfected) seeds do not contain any residues. Examples include warm water treatment or treatment with TSP or HCl. These products are not expected to affect the tests.

The tests used for seed health have been developed and validated for untreated seeds. Seed treatments can affect the reliability of the health test results. For this reason, preferably submit untreated seed samples. If there is an express wish/necessity to test treated seeds, a comment on the certificate will state that the test has only been validated on untreated seeds.

This is not applicable to tests that explicitly state that the test is performed on treated seed. Please state the type of seed treatment applied when submitting the sample.

This plays a less important role with quality tests (germination power, purity etc.).

The tests used for seed health have been developed and validated for untreated seeds. Seed treatments can affect the reliability of the health test results. For this reason, preferably submit untreated seed samples. This especially applies to tests performed using a culture method. The number of microorganisms in the seed increases sharply during the priming process. These additional microorganisms in the seed disrupt the test to such an extent that, even after additional disinfection after priming, no assessable results can be obtained.

This plays a less important role with quality tests (germination power, purity etc.).

Unfortunately there are two reasons that prevent this:

• Naktuinbouw has no facilities for the application of disinfectants, other than those necessary to perform the test.
• If a sample is disinfected, it is no longer the actual sample that was submitted. As such, it is no longer representative of the lot from which the sample was taken.

We are only allowed to receive and test the samples if seed lots have been treated with Thiram and are going to countries outside the EU.

Samples intended for health tests cannot be returned. First of all, these samples are tested destructively. After testing, the samples are no longer usable. Secondly, they are in a contained area. The samples are not allowed to leave this area.

You will find our current portfolio in the Price list Laboratories 2024. For vegetable crops, which tests we can perform is stated per crop. For plant material, a separate chapter lists which tests are available.

When Pospiviroids test are requested, the seeds are tested for the following viroids:

• Columnea latent viroid (CLVd)
• Pepper chat fruit viroid (PCFVd)
• Potato spindle tuber viroid (PSTVd)
• Tomato apical stunt viroid (TASVd)
• Tomato chlorotic dwarf viroid (TCDVd)
• Tomato planta macho viroid (TPMVd)

If plant material is submitted, in addition to the viroids above-mentioned, tests are also performed for:

• Chrysanthemum stunt viroid (CSVd)
• Iresine viroid 1 (IrVd)
• Portulaca latent viroid (PoLVd)

A generic PCR test is available for testing for phytoplasmas. This can detect the following phytoplasmas:

• Apple proliferation phytoplasma; syn. Candidatus Phytoplasma mali
• Apricot chlorotic leafroll mycoplasma
• Aster yellows
• Elm phloem necrosis
• Elm yellows
• European stone fruit yellows; syn. Candidatus Phytoplasma prunorum
• Peach rosette phytoplasma
• Peach X disease phytoplasma
• Peach yellows phytoplasma
• Pear decline phytoplasma
• Pear decline phytoplasma; syn. Candidatus Phytoplasma pyri
• Potato stolbur
• Rubus stunt
• Strawberry green petal phytoplasma
• Strawberry witches’ broom
• Yellow decline of Lavendula

The Harper and Quyang method are both used to test for Xylella. Both are required by Australia. This means that our protocol complies with Australian requirements.

Samples with symptoms are tested by the Diagnostics department. Various techniques are used to detect and identify which pathogen is present. If you already suspect which pathogen(s) may be present, a specific test for those pathogens is also possible.

It is possible to make certain crops virus-free (strawberry, small fruit and woody fruit crops). See the price list Laboratoria 2024 for more details. For all other crops, please contact specialised tissue culture companies.

The laboratory has three different certifications/accreditations:

• NEN-EN-ISO 9001:2015
• NEN-EN-ISO/IEC 17025:2017
• ISTA Accreditation

You can find more information about our accreditations on our website.

For agricultural crops, please contact our fellow inspection service NAK in Emmeloord

Leave the lot for a few months, then send a sample again. Saprophytes cannot survive on bean seeds for long.

Saprophytic bacteria or fungi are harmless organisms that sometimes naturally occur on seeds. If these saprophytes are present in high numbers, this may disturb the culture method. This means there is a considerable risk that an assessment of that test will no longer be possible.

Drying after HCl treatment must be done quickly. If the drying process takes too long, the risk of saprophytic bacteria and fungi growing is too high.

Pectinase treatment is also an option. This is faster and reduces the exposure time and the growth of saprophytes.

The test where this is mentioned is the basic test. Suspicious values were found in this test and a (an additional) validation test was performed. You can find this on the certificate with the same sample, but it states a different technique. The result of this is leading.

Certain amendments can be made after a certificate has been issued. Please send a request to Laboratory Support team: laboratoria@naktuinbouw.nl.

According to our ISO certification, we are obliged to change the version number on the new certificate. It also states which amendments have been made.

No specific directives or legislation apply. The specific requirements are set by companies themselves.

The Price list Laboratories 2024 states the duration of the tests. Tests generally start within three weeks of receiving the samples. However, this time may differ if a high number of samples are submitted. MyNaktuinbouw shows the expected end date and any results of your completed test(s).

NAL stands for Naktuinbouw Authorized Laboratory. This means that Naktuinbouw authorises companies to test their own lots of material. The certificates issued by these companies are accepted in the same way as a Naktuinbouw certificate for the purpose of obtaining a phytosanitary certificate.

Naktuinbouw does not issue NAL certificates.

Samples can be sent by PostNL to:

Testing Laboratory
Attn. Laboratories Administration
P.O. Box 40
2370 AA Roelofarendsveen, NL

Diagnostics
Naktuinbouw
Attn: Diagnostics
Sotaweg 22
2371 AA Roelofarendsveen, NL

Variety Tracer
Naktuinbouw
Attn: Variety Tracer
P.O. Box 40
2370 AA Roelofarendsveen

When sending the samples with a courier service, or in case of large quantities of samples (e.g. on a pallet), please use the visiting address:

Testing Laboratory
Naktuinbouw
Attn: Laboratory Administration
Sotaweg 22
2371 GD Roelofarendsveen

Diagnostics
Naktuinbouw
Attn: Diagnostics
Sotaweg 22
2371 GD Roelofarendsveen

Variety Tracer
Naktuinbouw
Attn: Variety Tracer
Sotaweg 22
2371 GD Roelofarendsveen

Samples can be received between 8:00-17:30, from Mondays to Fridays.

Bioassays
Samples may be sent to:

Naktuinbouw
Tienrayseweg 9a
5961 NK Horst

A submission form downloaded from the website. We have three different submission forms:

1. For plant material with symptoms
2. For plant material without symptoms
3. For Seed samples

Samples submitted from outside the EU must be accompanied by a phytosanitary certificate or DOIV.

You can find this form on the website. There are three different types:

• For plant material with symptoms
• For plant material with no symptoms
• For seed samples

A phytosanitary certificate is sometimes required for samples submitted from outside the EU. If it is not possible to request a phytosanitary certificate, you can request a special, accompanying letter (DOIV) on the website.

We advise you to send plant samples (perishable material) without symptoms on Mondays or Tuesdays. Plant samples with symptoms can be sent from Mondays to Thursdays. This will avoid samples being left in the post over the weekends and not being stored in the correct conditions. Samples sent on these days will also arrive in time for testing.

Seed samples can be sent every day of the week.

A registration form must be filled in first so we can enter the necessary company details in our system. 

If the different crops are in the same package, one DOIV is sufficient. A separate DOIV must be requested for each shipment.

A DOIV must be requested if it is not possible to request a phytosanitary certificate. The application must comply with the following criteria:

• The crop/family is not stated on the EU list of banned plants, unless indicated that the material is intended for planting up.
• The material is used for destructive testing.
• The material is sent directly to the Netherlands from the country of origin, without transhipment in another country.

A DOIV is a document issued by the Netherlands Food and Consumer Product Safety Authority (NVWA). This document permits plant material without a phytosanitary certificate to be imported for the purpose of destructive testing on samples. The Dutch customs authorities required this document to release the shipment.

Samples can be sent by PostNL to:

Testing Laboratory
Attn. Laboratories Administration
P.O. Box 40
2370 AA Roelofarendsveen, NL

Diagnostics
Naktuinbouw
Attn: Diagnostics
Sotaweg 22
2371 AA Roelofarendsveen, NL

Variety Tracer
Naktuinbouw
Attn: Variety Tracer
P.O. Box 40
2370 AA Roelofarendsveen

When sending the samples with a courier service, or in case of large quantities of samples (e.g. on a pallet), please use the visiting address:

Testing Laboratory
Naktuinbouw
Attn: Laboratory Administration
Sotaweg 22
2371 GD Roelofarendsveen

Diagnostics
Naktuinbouw
Attn: Diagnostics
Sotaweg 22
2371 GD Roelofarendsveen

Variety Tracer
Naktuinbouw
Attn: Variety Tracer
Sotaweg 22
2371 GD Roelofarendsveen

Samples can be received between 8:00-17:30, from Mondays to Fridays.

Bioassays
Samples may be sent to:

Naktuinbouw
Tienrayseweg 9a
5961 NK Horst

• Take samples from a spot where the new symptoms are visible. It is often not possible to run laboratory tests on plants that have died off completely.
• Take a sample before any pesticides/crop protection agents are applied. Pesticides can destroy or mask the symptoms caused by pathogens and interfere with the laboratory tests.
• If the symptoms are unclear, send us the entire plant.
• Where symptoms are unclear, or in the case of a rare plant, please also send us part of a healthy specimen. Pack the healthy sample separately and indicate on the label that it is healthy material.
• If it is impossible to send a sample immediately, keep it cool. Never place samples in direct sunlight.

A submission form downloaded from the website. Samples submitted from outside the EU must be accompanied by a phytosanitary certificate or DOIV.

You can find this form on the website. There are three different types:

• For plant material with symptoms
• For plant material with no symptoms
• For seed samples

A phytosanitary certificate is sometimes required for samples submitted from outside the EU. If it is not possible to request a phytosanitary certificate, you can request a special, accompanying letter (DOIV) on the website.

We advise you to send plant samples (perishable material) without symptoms on Mondays or Tuesdays. Plant samples with symptoms can be sent from Mondays to Thursdays. This will avoid samples being left in the post over the weekends and not being stored in the correct conditions. Samples sent on these days will also arrive in time for testing.

Seed samples can be sent every day of the week.

A registration form must be filled in first so we can enter the necessary company details in our system. 

It is also important to send an order form with the samples. This form is also on our website.

The Price list Laboratories 2024 states our standard portfolio of tests. For export purposes, some countries require tests for which no validated protocol is available. In exceptional cases, based on our experience and knowledge of crops and pathogens, we can create a customised test. If the test proceeds as expected, the result can be used for export purposes.

To request a test, please contact the Front Office of the laboratory.

It is possible to make certain crops virus-free (strawberry, small fruit and woody fruit crops). See the Price list Laboratoria 2024 for more details. For all other crops, please contact specialised tissue culture companies.

No specific directives or legislation apply. The specific requirements are set by companies themselves.

Here you can find the current list of fees of Naktuinbouw Laboratory:

Price list Laboratories 2024

You ask the laboratory for this letter by completing this form. When importing plant or seed samples for destructive testing from outside the EU (third countries), a phytosanitary certificate or an accompanying letter from the NVWA is required.

To register as a Naktuinbouw customer to use our Variety Testing services, please complete this form.