Breeder's co-trials vegetable crops

DUS testing for vegetable crops usually takes two years.
The examination is based on CPVO protocols and UPOV guidelines, which state that two independent trials (growing cycles) are necessary.

Only the results of tests performed by Naktuinbouw or another official agency are valid for both Dutch and European Plant Breeders’ Rights. For the purpose of listing, one of these two trials may be performed by the applicant. This is what we call the breeder's co-trial. If you want to apply for Plant Breeders’ Rights too, additionally an extra official trial is needed.

Advantages of breeder's co-trials

  • Cost saving. A breeder's co-trial can save costs, because in principle the costs involved for the second year of trials at Naktuinbouw are no longer necessary.
  • Time gain. As both the Naktuinbouw trial and the breeder's co-trial take place in the same year (1st year) the trial DUS examination can be completed more quickly.

Disadvantages of breeder's co-trials

A basic fee applies for performing a breeder's co-trial. Correctly setting up and performing a breeder's co-trial involves certain costs.

For the following reasons, the breeder's co-trial may also fail to provide sufficient results to enable the trial to be completed after one year:

  • Insufficient uniformity
    If uniformity in the Naktuinbouw trial and/or the breeder's co-trial is not sufficient, Naktuinbouw has to perform a third trial.
  • Insufficient confirmation
    If the results of the Naktuinbouw trial and the results of breeder's co-trial fail to confirm each other sufficiently, or if the new variety is barely distinct from the similar variety, Naktuinbouw has to perform a third trial. This is a regular occurrence, especially in crops with many close varieties.
  • Incomplete breeder's co-trial
    A similar variety to be used for comparison in the breeder's co-trial may possibly be unavailable because it is still being tested. Applications with an earlier date of application take precedence. For reasons of confidentiality, we cannot provide any information about applications that are being tested. It is possible that the variety that has precedence still has to be included as similar variety in a follow-up trial.


For multiple crops, the process can also be completed quickly by performing two official tests at Naktuinbouw, UKZUZ (Czech Republic) or UKSUP (Slovak Republic) in one year. 

Performing a breeder's co-trial

Do you want to set up a breeder's co-trial? Please indicate this on the application form. As from 1 March 2021 you can decide to assess the trial yourself or have assessment carried out by the Naktuinbouw inspector. As from 1 March 2021 different fees apply in this case . If the trial site is located abroad, you must always assess the trial yourself.  You assess the distinctness and uniformity and provide evidence in the form of photographs to support your observations.

Requirements placed on breeder's co-trials

The trial set up must meet the following requirements:

  • The number of plants must comply with the CPVO protocol or UPOV guideline relevant to that crop, including the number of replicates stated. The protocol or guideline to be used can be found on the CPVO website. Preferably use the same seed lot as the sample used for identity.
  • Naktuinbouw will inform you about the similar varieties, all of which must be included in the trial. If this is not possible for one or more varieties, an additional year of trials may be required. The costs of this additional year of trials are for the applicant. If you have indicated your intention to assess the trial yourself, Naktuinbouw will send you an assessment form. Use this form to enter the following information:
    • information about the trial (such as sowing date, date of assessment and number of plants)
    • your observation of off-types (number, type)
    • your observation of the differences compared with the similar varieties.
  • If you assess the trial yourself, you must provide evidence in the form of photographs to support your observations. This means an overview of the trial, photographs that clearly show the candidate variety and the similar variety/varieties and an overview of the candidate variety showing the uniformity.
  • The results of the breeder's co-trials must be received by Naktuinbouw before the closing date of the next year (see the ‘closing date’ in S2/S3 on the CPVO website, here you can search using the Latin crop name and examination office Naktuinbouw).
  • If you have indicated that you want Naktuinbouw to assess the trial, arrange a suitable date with the inspector. In this case too, the results must be available before the closing date of the next year.