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THE INSPECTION OF DUTCH SEED POTATOES;The importance of approval
THE INSPECTION OF DUTCH SEED POTATOES;
The importance of approval
Contents The importance of approved seed potatoes 4Minimum quality requirements 5Major advantages 5Who monitors and inspects the quality of Dutch seed potatoes? 6
Diseases 8Virus diseases 8Bacterial diseases 9
Clonal selection and classification 12Clonal selection system 12Classification 13
NAK inspection requirements are stringent 15A statutory basis 15The inspection process 17
Field inspections 19Varietal purity 19Diseases 20Other factors 20Haulm destruction at the right time 21
Post-harvest inspections 23
Lot inspections 25Tighter standards 26Phytosanitary aspects 26
Different customers, different requirements; a comparison 29
The certificate/plant passport 31Statutory requirement 31Information on the certificate 31Inspected and approved Dutch seed potatoes 32
Appendix 34ELISA test 34
Colophon & Addresses 36
The importance of approved seed potatoesThere can be no doubt that potatoes are of significant economic andnutritional importance to the producers and consumers of manycountries. One of the major benefits of potatoes is that they can beutilised in many different ways. But while potatoes are very versatile andinteresting, they are also susceptible to many pests and diseases. Theseoccur in all areas where potatoes are grown. Some are soil-borne, butmany diseases are also transmitted by seed potatoes. Many of thewidespread diseases are regarded as quality diseases. Examples of theseare late blight, scab, rhizoctonia canker, blackleg, fusarium and severalvirus diseases. Infections of such quality diseases in seed potatoes are onlyallowed to a very limited extent. In addition to quality diseases there arequarantine diseases. These are diseases that are assumed to be sodangerous that they must not be allowed to occur in seed potatoes at all(for example golden nematode, brown rot and ring rot). Besides soil-borne diseases there are diseases that can infect potato plants via adifferent route. The most important are the fungus disease late blight,
which is transmitted through the air via spores, and diseases caused byviruses which are transmitted by aphids (e.g. leafroll and potato virus Y).The larger the number of sources of infection in the basic stock, thegreater the damage these diseases may cause. So it is important to
It is impor-tant to minimi-se the numberof sources of
infection aseffectively as
possible. Oneof the best
ways of doingthis is by usingapproved seed
minimise the number of sources of infection as effectively as possible.One of the best ways of doing this is by using approved seed potatoes.
Minimum quality requirementsApproved seed potatoes must comply with a wide range of requirements.Individual countries formulate their own requirements for seed potatoes.After all, different buyers have different wishes. However, the EuropeanUnion (EU) has laid down minimum quality requirements for seeds andseed potatoes to co-ordinate the demand and supply as effectively aspossible. These requirements hold for all seeds and planting materialtraded within the EU. All seed potatoes traded in the EU member statesmust comply with at least these EU minimum requirements. Theindividual member states may use stricter national requirements if theywish. For its part, the Dutch seed potato sector has laid down stringentnational requirements in collaboration with the NAK and the Dutchgovernment. These high standards have earned the Dutch seed and seedpotato sector a strong competitive position.
Major advantagesThe Dutch agricultural sector is able to comply with these strictrequirements thanks to a number of major advantages, such as afavourable climate, an almost perfect soil and the high level of expertise
The Dutchagricultural hasa number ofmajor advanta-ges, such as afavourable cli-mate, analmost perfectsoil, the highlevel of experti-se of the gro-wers and a longtradition ofrecord keeping,inspection andregistration.
of the growers. Other great advantages in the Netherlands include thegood relations with the relevant agricultural organisations and anexcellent infrastructure. Moreover, Dutch agriculture also has a longtradition of record keeping, inspection and registration.
Who monitors and inspects the quality of Dutch seed potatoes? The NAK, the Dutch General Inspection Service for Agricultural Seed andSeed Potatoes, has many years experience in inspection and certification.Indeed, it has been doing this work since 1932 - and with evident success,
because the quality of Dutch basic stock is highly appreciated. Every year,seed potatoes from between 35,000 and 40,000 hectares are multipliedand inspected. Dutch seed potatoes are high-quality products, for whichthe demand is steadily increasing. Of course, Dutch seed potatoes do notowe their favourable position to the NAK alone. Their excellentreputation is based primarily on the high level of expertise of the manypeople involved in their production, from the breeders and growersthrough to the traders. Together they produce the high-quality seed andseed potatoes that meet the stringent requirements in the areas of health,varietal purity and physiological capacity. This is why buyers all over theworld have great confidence in the product, which is partly due to theindependent inspections of the NAK, the organisation that monitors theproducts quality.
The Plant Protection Service (PD) of the Dutch Ministry of Agriculture,Nature and Food quality also plays an important part in monitoring thequality of Dutch seed potatoes. This service is responsible for controllingquarantine diseases in the Netherlands and performs the phytosanitaryinspections for the presence of quarantine and quality diseases to which allbatches intended for export outside the EU must be submitted.
Decisive factors as far as the quality and vitality of seed potatoes areconcerned are: health varietal purity physiological condition
This brochure discusses these factors in various chapters, successivelyfocusing on diseases (virus and bacterial diseases), clonal selection andclassification, field inspections, post-harvest inspections, lot inspections,the standards employed in the Netherlands in relation to the EUstandards, and the NAK certificate/plant passport.
The brochure The Inspection of Dutch Seed Potatoes; The importance ofapproval is a joint publication of the NAK and the NIVAP.
NAK: Nederlandse Algemene Keuringsdienst voorzaaizaad en pootgoed van landbouwgewassen(Dutch General Inspection Service for AgriculturalSeed and Seed Potatoes), Emmeloord, theNetherlands.
NIVAP: Nederlands Instituut voor Afzetbevorderingvan Pootaardappelen (Netherlands Potato Consultative Foundation),Den Haag, the Netherlands.
8DiseasesVirus and bacterial diseases are the most important diseases that have tobe taken into account in the cultivation of seed potatoes in theNetherlands.
Virus diseasesThe most important virus diseases occurring in the Netherlands are thediseases caused by the leafroll virus and potato viruses Y (especially Yn),X and A. Of lesser importance are the potato virus S and the tobaccorattle virus. The symptoms that these viruses can cause differ substantially
Important facts on virus diseases:
Viruses are transmitted by seed potatoes; They are usually transmitted by aphids, but sometimes also by
contact (viruses X and S) or by nematodes (tobacco rattle virus); It takes some time for a virus to reach the tubers and for an
infection to result in symptoms; The susceptibility and vulnerability to viruses differ from one
potato variety to another and older crops are less susceptible thanyounger crops (maturity) resistance;
Each virus comprises several strains.
9and depend on the type of virus involved, the virus strain, the potatovariety and the growing conditions. The only way of finding out whichvirus has caused particular symptoms is by carrying out laboratoryanalyses (ELISA tests, see Appendix).
Bacterial diseasesThe pathological bacteria that are found in the Netherlands and belong tothe so-called Erwinia complex are distinguished on the basis of thesymptoms caused by these bacteria, notably blackleg and stem wet rot.The quality of a batch of seed potatoes is greatly dependent on thepresence or absence of these bacteria. Therefore, it is of great importance
that bacterial diseases are effectively controlled during the cultivation ofseed potatoes. Bacterial diseases are transmitted by infected seed potatoes,but it is by no means always possible to detect a bacterial infection in thefield or in tubers. That is why we speak of latent (hidden) infections.
Various factors occurring during the growth of a crop, harvest or storagecan cause the number of bacteria present in a crop to increasesubstantially. Indeed, the number of bacteria present in some tubers maybecome so great that the disease will be visible in the field in the next crop.
Unfortunately it is impossible to predict how long it will take for a latentinfection to become visible. The factors involved are too complex. Whatwe do know for certain is that an infected batch always involves a certainrisk. Fortunately, it is possible to minimise the spread of an infection by
adhering to specific cultivation, harvesting, storage and handlingtechniques. This way it is also possible to prevent the risk of newinfections or re-infection. There are no agents that are capable