Potato seed tubers can be affected by many fungal, bacterial and viral pathogens which may adversely influence emergence and crop yield. Some seed borne diseases also reduce the value of ware as a result of blemishing.
Assessment of fungal, bacterial and viral infection of seed samples enables high quality seed to be identified, highlights potential problems and indicates where use of fungicide may be beneficial. Assessment of virus incidence is particularly important for home saved seed and selecting stocks for growing seed. Germination testing can identify stocks which may emerge irregularly or incompletely.
Seed samples submitted for disease assessment are examined both macroscopically and microscopically for all common potato pathogens and any physical or pest damage to the seed is also recorded. For surface diseases, both the incidence (% of tubers affected) and severity (extent of surface infection on the tuber) are recorded. Plugs of potato, including the buds from the seed tubers are incubated and examined microscopically to determine the incidence of fungi which may not be apparent macroscopically (including the fungi causing black scurf / stem canker, black dot, silver scurf and skin spot). Ware samples can also be submitted for detailed quality assessment.
Important diseases assessed include:
Black Scurf, Dry Rot, Gangrene, Powdery Scab, Silver Scurf and Skin Spot
For assessing the incidence of virus in potato seed, plants are grown from the sample submitted and sap from the leaves of each test plant is tested separately using a serological technique (ELISA). Breaking dormancy, growing plants and testing is usually completed within 6-8 weeks. The ELISA test can detect all common potato viruses and determine the extent of infection by tobacco veinal necrosis virus (PVYN) a distinct strain of PVY separately from other strains.
Tests are offered for the following viruses:
Potato leafroll virus (PLRV)
Severe mosaic (PVY, PVYN)
Mild mosaic (PVX)
PVS, PVA, PVV
A sample of seed tubers is placed in a controlled temperature cabinet and sprouting recorded at regular intervals to indicate the variation in sprouting and any tubers which fail to sprout.
Seed samples should consist of 100 (Disease Assessment and Germination Test) or 105 (Virus Assessment) tubers selected to be representative of the whole seed bulk. Random sampling is very important to obtain an estimate of disease representative of the stock. If more than one test is required for a single stock please supply sufficient tubers for each test in separate bags.
To discuss the relevance of different virus tests, please contact David Firman, 01223 651599, firstname.lastname@example.org
A form for indicating test requirements and listing references to identify stocks should be supplied with the sample(s).
|Disease Assessment (Fungal & Bacterial)|
|Standard macroscopic and microscopic test||£50.75|
|Macroscopic test only||£37.00|
|Post-harvest seed testing|
|Standard test for PLRV & PVY (L+Y)||£145.00|
|Additional cost per virus for PVYN, PVX||£26.00|
|6 virus test (PLRV, PVY, PVX, PVS, PVA, PVV)||£216.50|