Potato disease testing

Virus testing

Virus testing can be done on leaf or tuber material; Niab recommends testing a sample size of 100 leaves or tubers and ask for 110 tubers to be submitted. The submitted sample should be taken throughout the field to give a representative sample, rather than taking from a small part of the bulk which will give a biased view of the level of virus in the crop.

Niab can test by either ELISA and RNA-based methods. The ELISA method uses specific antibodies to attach to the protein coat of the virus and, using a colour change reagent, the virus is detected. It requires leaf material, which means growing tubers in controlled glasshouses for about eight weeks until there is enough material to test in the laboratory.

Plant with Potato virus Y

The RNA method is a lot quicker as material can be used direct from the tuber, taking around five days to complete. The test extracts virus RNA from the plant material which is then quantified.

Niab can test up to seven different viruses: Potato virus Y and the Potato virus Yn strain, Potato Leaf roll virus (PLRV), Potato virus A, Potato virus S, Potato virus V and Potato virus X. The most common virus found is Potato virus Y.

Fungal diseases

Silver scurf on potato surface

Fungal diseases, such as silver scurf, black dot and black scurf, can bedetected on the surface of the tuber. Niab offers a test to determine the incidence and surface area coverage of the diseases. 

There are two tests for fungal diseases – a visual whole surface tuber test and a microscopic analysis. The whole tuber test is carried out first, with an examination of the entire surface area of the tuber to determine the percentage coverage of the disease.

For a more thorough result microscopic analysis is carried out. The main apical eye is removed from the tuber, with the remaining pieces left in a temperature-controlled incubator, with lights, for seven days to allow the disease develop. It is then examined under a dissection microscope to identify and quantify the diseases present.

Plant with potato leaf roll virus

Germination testing

Niab recommends sending in a sample of 100 tubers after harvest. The whole tubers are incubated with lights and a constant temperature to help sprouting. The tubers are monitored weekly for signs of growth and the number of sprouts reaching the right criteria are recorded.

The test is complete when all tubers have sprouted. This can take anything from 3 to 12 weeks to complete depending on variety and if the seed has been exposed to any treatments. The customer report shows the germination progression graphically.

The test will show the vigour of the potato seed and the test indicates which stocks will emerge irregularly or have incomplete emergence. Tuber age is an important factor in this test; stocks received in November may start to germinate at the same time as stocks received in September when planted at the same time

Send us your samples

Potato testing mainly occurs between September and March. For the latest prices, samples and delivery:

More details

This article originally appeared in the Spring 2025 edition of Niab’s Landmark magazine. Landmark features in-depth technical articles on all aspects of Niab crop research, comment and advice. You can sign up for free and get Landmark delivered to your door or inbox:

Sign up