Definition

Potato cyst nematodes (PCN), commonly associated with potato fatigue, are microscopic roundworms that attack potato roots. They belong to two species:

• Globodera rostochiensis (Ro)
• Globodera pallida (Pa)

Both species include groups called pathotypes, which differ in their ability to reproduce on resistant potato varieties.

Importance

PCN infestations can severely reduce potato yield and quality. They persist in soil for years and are difficult to eradicate, making species identification and resistance management essential for sustainable potato production.

Pathotypes

• G. rostochiensis: Five pathotypes (Ro1–Ro5), with Ro1 being most common and Ro4/Ro5 least frequent.
• G. pallida: High variability among populations, but no clearly defined pathotypes.

Most starch potato varieties are resistant to both species, but some are only resistant to one species or specific pathotypes.

Resistance in varieties

• Many consumer varieties now offer resistance to both species.
• Effectiveness against G. pallida varies by population and field conditions.
• Mixed infections of different pathotypes can occur, so monitoring is crucial.

Species determination

If PCN is detected, species identification is vital for selecting the right variety.

PCR testing is the most reliable method, using DNA analysis to distinguish species.

This technique allows testing of large numbers of cysts accurately.

Variety selection and cropping strategy

Resistance level required depends on:

• Rotation frequency
• Aggressiveness of nematode population

Recommended Relative Susceptibility (RH) values:

1 in 2 rotation: RH ≤ 10%

1 in 3 rotation: RH ≤ 15%

1 in 4 rotation: RH ≤ 25%

1 in 5 rotation: RH ≤ 37%

Symptoms in the field

• Slowed growth, irregular oval drop spots
• Smaller plants in centre, larger on edges
• Delayed crop closure and uneven flowering

Recognition on roots

From mid-June: white globules (cysts) visible on roots of susceptible varieties

Colour changes:

• G. pallida: white → brown
• G. rostochiensis: white → yellow → brown

Note: Resistant varieties may show few cysts, but damage can still occur.

Source: Actieplan Aaltjesbeheersing. Het Actieplan is een initiatief van het voormalige Productschap Akkerbouw en LTO Nederland.

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