The Seed Potato Classification Scheme (SPCS) ensures the continuing high quality of Scottish Seed Potatoes, by setting strict tolerances for freedom from disease and trueness to type. SASA is the Certifying Authority for the SPCS and also carries out a range of scientific activities in support of seed potato classification in Scotland.
Information on the SPCS, including application forms for tuber inspection and soil testing for PCN, can be found in the Classification Scheme section.
Most Scottish seed potatoes are derived initially from pathogen-tested microplants held in SASA's nuclear stock unit.
Our activities with regard to PCN and aphids are supported by an active research programme, see the PCN research page.
SASA also conducts supporting work on potato diseases affecting classification and export seed potatoes. View a list of recent publications.
Information on new potato varieties listed recently in the UK National List can be obtained under new varieties. Other information on potato varieties can be found on the European Cultivated Potato Database website. SASA also provides a service to identify potato varieties by DNA fingerprinting using a growing database of over 1,000 potato varieties for comparison including all UK national listed varieties.
See the Potato Training Courses page for information on courses available from SASA.
Scotland is a major producer of quality seed potatoes. Seed potatoes produced and marketed in Scotland must be classified under the Seed Potato Classification Scheme (SPCS). SASA is the Certifying Authority for seed potatoes in Scotland and this section gives information on seed potato classification (certification).
Before seed potatoes can be marketed they must meet the requirements of the Seed Potatoes (Scotland) Regulations 2000 and The Seed Potatoes (Scotland) Amendment Regulations 2005 and 2007 which also implement the requirements of EC Council Directives 93/17/EEC and 2002/56/EC and Land Commission Decision 2004/3/EC.
Further detailed information on seed potato classification in Scotland and the requirements to be met by Scheme applicants can be found under the appropriate heading on the menu opposite. Conditions applied to exports of Scottish seed potatoes to non-EU countries can be found on the Potato Export Conditions page.
Each year a Register of Seed Potatoes is published in October and this gives detailed information on seed crops for which Inspection Report Forms have been issued by SASA.
For further information and forms, please see the links below:
Information gathered and held by SASA is covered by current disclosure legislation; please see the SPCS Disclosure Statement page for more details.
To contact SPCS, see the Contacts - Potato Branch page.
Handling procedures for information received in relation to the classification of seed potatoes have been designed to take into account legislative developments, particularly the Freedom of Information (Scotland) Act 2002, the Environmental Information (Scotland) Regulations 2004 and the Data Protection Act 1998. Applicants should be aware that from the growing season 2007 onwards it is the Certifying Authority's intention to publish details of all crops in the Register of Pre-basic and Basic Seed Potato Crops. The following statement will now appear on the relevant forms "The Certifying Authority is bound by current disclosure legislation. All crops which meet Pre-basic and Basic requirements at crop inspection will appear in the Register of Pre-basic and Basic Seed Potatoes."
The Certifying Authority may be required to release information, including personal data and commercial information, if requested under the Environmental Information (Scotland) Regulations 2004 or the Freedom of Information (Scotland) Act 2002. The Certifying Authority will not permit any unlawful breach of confidentiality nor permit breach of obligations under the Data Protection Act 1998.
Detection and identification of a range of potato pathogens is carried out at SASA, mainly in support of plant health regulations and the SPCS.
Testing to the same standard is also carried out on a commercial basis. Main categories of testing include:
Virus testing in support of growing crop inspections
Bacteriology in support of the SPCS and Plant Health.
SASA is also a source of expert knowledge of and testing for tuber storage diseases.
SASA has a wide range of expertise in fungal disease diagnosis and epidemiology and has considerable experience in development work on a range of diseases.
Development activities cover a wide range of diseases. For example, past studies have identified the store as a source of contamination for healthy stocks by a number of pathogens; spread of gangrene fungus in aerosols generated by rain; effectiveness of various fungicides controlling tuber rots and blemish diseases; detection of fungicide resistant strains; survival of potato pathogens in field soils, development of test methods to recover tuber pathogens from soil and characterisation of late blight populations in Scotland.
This work has involved a range of collaborators: IACR Rothamsted, James Hutton Institute, ADAS Consulting Ltd.
View a list of SASA publications on tuber diseases.
The Nematology Laboratory at SASA provides technical support through the detection and identification of plant-parasitic nematodes (eelworms). Our work of the Laboratory supports the Scottish Government's Plant Health Service in the implementation of the plant health regulations and through meeting the requirements of the Seed Potato Classification Scheme (SPCS). The Scottish potato industry benefits from the production of seed potatoes that meet high standards of plant health, minimising the loss of quality and yield that these pests can cause.
The Nematology Laboratory is able to offer the following services in relation to the diagnoses and control of Potato Cyst Nematodes:
Take a handful of soil from almost anywhere in the world, from the Arctic to the Tropics, from the tops of mountains to the depths of seas, from deserts to swamps, extract the living organisms in water, and among the other forms of life you will find elongate, threadlike, active animals – these are nematodes (or eelworms, or roundworms). Many of them will just be visible without magnification, but others will only be seen with a good magnifying lens or microscope.
Or, if you catch a fish, bird, or mammal, dissect out its stomach or intestine, in most cases you will find some nematodes living there.
Nematodes (the name is derived from the Greek word for thread) are elongate, tubular organisms that move like snakes or eels. They are aquatic and live in marine or fresh water, and in films of water within soil/compost/forest litter/moss etc. They are one of the most successful and adaptable of animal groups, being rivalled only by insects as regards range of habitats or number of species.
Most species are free-living, with their food consisting of micro-organisms – fungi, bacteria, and algae, and these play an important role in decomposition and recycling of nutrients. Nematodes occur in soil in great numbers-rich arable soil may contain 3 billion (3,000,000,000) nematodes per acre (0.4 hectares), calculated to a depth of 20 cm.
Many nematodes are highly successful parasites. The first recorded ones were, not surprisingly, human parasites. Passages in the “Papyrus Ebers” (dated 1550 BC) are said to contain reference to the human intestinal parasite, Ascaris lumbricoides, and the tissue parasite, Dracunculus medinensis, (the Guinea Worm), both of which are large parasites which may exceed a foot in length. The Guinea Worm is believed to have been the fiery serpent of the bible which plagued the Children of Israel after their journey through the swampy regions near the Red Sea. Certainly this pest is still found there today.
Many of these animal parasites have intricate life cycles during which the parasites alternate between their vertebrate hosts and invertebrates such as arthropods and crustacea.
Although nematodes have undoubtedly been associated with plants for thousands of years, the first plant-parasitic nematode was reported in 1743 by an English clergyman, Needham. He was examining some dry, diseased wheat kernels in a drop of water, and after a time, to his amazement, he saw a mass of fibres that began to twist. He wrote:
“I am satisfied that they are a species of aquatic animal and may be denominated worms, eels, or serpents, which they much resemble.”
Whereas animal parasitic nematodes may be large, (the largest of all being Placentonema gigantissima, a monster nine metres long found in the placenta of sperm whales), the plant parasites are mainly microscopic. The largest, the longidorids, are 5-10mm long, but many nematodes are shorter than 1 mm. Being slender and transparent, they cannot often be seen by the naked eye.
Other groups of worms may be confused with nematodes. These include flatworms, (Platyhelminthes), e.g. liver flukes, which are flattened and oval in shape; tapeworms (Cestodes), most of which are adapted for living in the gut of vertebrates and have a body of rectangular flattened segments with suckers and hooks at the anterior end; and earthworms, which are long and segmented. The white, wriggling worm-like organisms, commonly seen in rotting plant material or compost, are seldom nematodes. With a few exceptions, if you can see an organism, with the naked eye, it is not a plant-parasitic nematode.
Although nematodes are typically worm-shaped, in one particular group of plant-parasitic nematodes the cuticle of the females develops into a tough wall creating a spherical, or near-spherical, cyst protecting the female’s fertilised eggs. These cyst nematodes are the most economically important nematode pests of temperate agriculture. The potato cyst nematodes, Globodera pallida and Globodera rostochiensis, introduced into Europe with potatoes from South America, have subsequently spread throughout most of the potato growing areas of the world. They are treated as quarantine pests because of the economic damage they cause and the difficulties faced when eradication is attempted.
Potato cyst nematodes (PCN) comprise of two very closely related species (Globodera rostochiensis, Globodera pallida) which co-evolved with the potato in South America, but have subsequently been introduced elsewhere with the production of potatoes. Outbreaks of potato cyst nematodes have now occurred in most of the potato growing areas of the world. Probably the only country in the world growing a large acreage of potatoes that has yet to report an outbreak of PCN is China. Reports of PCN remain scarce from some countries with extensive potato acreages, most notably Australia, Canada, USA, India and, probably, some parts of the former USSR. PCN continues to be a quarantine pest throughout the world.
Symptoms of PCN attack on potatoes reflect those of plants with an inefficient roots system i.e. poor growth, wilting during periods of water stress, early senescence and reduced tuber yield up to levels in excess of 80%. Although most PCN development occurs within the root system, the cyst mature outside the roots and then fall into the soil at harvest, making them easily transported within soil attached to tubers, especially in natural crevices such as tuber eyes. Only under exceptional circumstances, e.g. at very high densities, will cysts be found directly attached to potato tubers.
The main route by which PCN spreads is through the movement of infested material, primarily soil which may be transferred with tubers, plants, waste material or farm machinery. The higher the population of PCN in a field, the greater the risk of spreading it to other land. However, if potatoes are grown in soil infested with PCN, the risk of transmission with tubers from such a crop can also be reduced by minimising the quantity of soil associated with those tubers. Therefore, the key principles of PCN control are targeted at seed potatoes: ensuring that the land on which the seed is grown has been tested and the sample has been found to be free from PCN prior to planting and that a low tolerance (1%) is set for soil associated with seed potatoes for marketing.
In the EU, one major step forward in PCN control from the old 1969 PCN Directive to the new 2007 Directive (2007/33/EC ) relates to the definition of seed potatoes. For the purposes of the 1969 Directive, the legislative controls on PCN related only to seed potatoes that were marketed. The 2007 Directive defines seed potatoes as any potatoes that will be planted, recognizing that the risk of spreading PCN relates to the movement of any planting material.
The 2007 EU PCN Directive requires Member States of the EU to submit annually a list of all new potato varieties which have found to be resistant to PCN by official testing. Until 2010, all cultivars of potato entered for the UK National List VCU (Value for Cultivation and Use) trials have been tested for resistance to the dominant pathotypes of PCN occurring in the UK. Under the new Directive all official testing for resistance will be harmonised, including assessing resistance by a common scoring system based on a 1 to 9 scale.
In the UK, testing for resistance to Globodera pallida (pathotypes Pal & Pa2/3) is conducted at two centres: Edinburgh (SASA) and Cambridge (NIAB). Testing for resistance to Globodera rostochiensis (pathotype Rol) is conducted at Edinburgh only.
Potato cyst nematode (PCN) is the name commonly given to two species of cyst nematode which are serious pests of potato crops world-wide, namely Globodera pallida and Globodera rostochiensis. They feed on the roots of the plant and can cause significant loss of yield, and the cysts can survive in the soil for many years, multiplying rapidly when a new crop of host plants is planted.
Taking effective action against PCN is vital to maintain supplies of both healthy seed potatoes for the ware industry in Scotland, and uncontaminated land for potato production.
The main methods of control are to ensure seed potatoes are produced in land free of PCN and, where PCN are found, to place restrictions on the use of the land and the disposal of crops, waste and soil to prevent the pest spreading.
PCN have been subject to controls under European legislation since 1969. A new PCN control Directive, came into force on July 1, 2010. This aims to strengthen and harmonise controls against PCN, taking account of changes in the understanding of the biology of the pest, its distribution across the EU and practices within the potato industry.
The Directive is implemented in Scotland by the Plant Health (Scotland) Amendment Order 2010, which was laid before the Scottish Parliament on May 21, 2010. Under the Plant Health Fees (Scotland) Amendment Regulation 2010, fees are now in place for PCN testing.
Under the new Directive 2007/33/EC seed potatoes must only be planted on land which has been found to be free from PCN infestation following an official soil test. Failure to pass this test results in the land concerned being ‘recorded' as infested with potato cyst nematodes. No seed potatoes may be grown in this land, either for inspection within the SPCS or for farm saved seed. Ware potatoes may be grown, but only if an Official Control Programme is in place. The land remains ‘recorded’ as infested until such time as a future official tests show that PCN are no longer present.
Growers wishing to produce seed potatoes, either for classification or for farm-saved seed which will be planted other than at the place of production, are requested to make an application for a soil test by 31 August of the preceding year. The application form and guidance for making an application are set out on the PCN Soil Testing documents page.
The new PCN Directive sets out a harmonised protocol for soil sampling for use by all EU Member States. Fields are sampled at a standard rate of 1500ml/ha or, if certain conditions are met which reduce the risk of PCN infestation, at a lower rate of 400ml/ha. These conditions relate to history of the land, either in relation to previous potato crops or PCN soil tests. Sampling is carried out by staff from the Scottish Government Agriculture and Rural Delivery Division Area Offices.
If you have any technical enquiries about soil sampling for PCN, please contact Jon Pickup. If you are enquiring about the results of any soil samples that you have applied for, please contact Seed Potato Classification Scheme.
After sampling, the soil is sent to the Nematology Laboratory at SASA. The laboratory is the single Scottish centre for the examination of all official PCN samples. Cyst nematodes are extracted from the soil samples using a carousel - an automated sieving and flotation technique.
Diagnoses from the extractions produced by the carousel will be carried out by one of two methods: visual examination and PCR.
Due to the conditions set out in the new PCN Directive which determine future sampling rates, the diagnoses for samples taken from land which has not previously had an official PCN test and samples from land for which a ‘derecording test’ has been requested are carried out by visual examination. These samples are examined under a low power stereo microscope at a magnification of x12.5. Any PCN cysts (Globodera spp.) are picked off and examined under higher power to check identification and viability. Juveniles and cyst walls of all Globodera are examined under a magnification of x1000 to differentiate between G. rostochiensis and G. pallida. If more than one live PCN cyst is present, the remainder are identified using a polymerase chain reaction (PCR) diagnostic technique developed at SASA.
The majority of samples will be diagnosed by PCR using a new method designed for use on the floats from soil samples. This method has the advantage of having been developed for high throughput and consequently provides the laboratory with the ability to provide PCN diagnoses much more quickly than the more traditional method of visual examination.
Certificates of clearance are issued via the team who administer the Seed Potato Classification
Scheme, who also deal with the recording of infested land.
If you have any technical enquiries about soil sampling for PCN, please contact Jon Pickup. If you are enquiring about the results of any soil samples that you have applied for, please contact Seed Potato Classification Scheme
Under the new PCN Directive 2007/33/EC, there is no longer a requirement to test samples of growing media (usually peat based) in which potato mini-tubers are grown, to confirm the absence of PCN. The new PCN Directive only relates to the testing of 'field-soil' used for growing seed potatoes.
No PCN have been found in tests of peat-based growing media carried out at SASA during the past 20 years, and it can therefore normally be considered to be "a pest-free growing medium" as required by the SPCS. If pre-basic growers involved in mini-tuber production wish to obtain a test on, for example, a new delivery of the growing medium, SASA can provide this service on a commercial basis. A fee of £14.00 plus VAT per sample of 400ml or less will be charged.
A representative 400ml sample should be submitted by the grower to the Nematology Laboratory at SASA. At the laboratory, peat samples are dried and then processed by centrifugation in a glycerol, ethanol and kaolin mixture. The supernatant is then passed through two sieves. The residue from the second and finer sieve is transferred onto filter paper and then examined visually for the presence of PCN. Results will normally be issued within 10 working days of receiving the sample.
If you have any technical enquiries about testing peat for PCN, please contact Jon Pickup. If you are enquiring about the laboratory results for any peat that you have had tested, please contact Yvonne Cole.
Most countries require imported potatoes, if not all plant material and soil, to be free from Potato Cyst Nematodes (PCN). For seed exports, a phytosanitary certificate issued on the basis of a pre-crop soil test is a generally accepted means of assuring PCN freedom. As PCN cannot be detected by the visual inspection of harvested tubers, standard pre-export inspection for health and quality cannot confirm the presence or absence of cysts. Cyst detection at this stage necessitates laboratory examination. Information on countries requiring pre-export consignment tests for PCN is available on the Potato Export Conditions part of the Scottish Government website.
The soil for a consignment test is collected from a representative sample of bags of tubers, by staff from the Scottish Government Agriculture and Rural Delivery Division Area Offices. The number of bags chosen is on a sliding scale, from a minimum of 5 bags at 5 tonnes, to 10 at 20 tonnes, with a further bag for each additional 10 tonnes. It is important to keep soil contamination to a minimum, although it can be difficult to reduce the amount of soil to the 'dusting' demanded by some countries. The Scottish Government operates to a maximum soil tolerance of 0.5% by weight.
At SASA, the sample is prepared for examination by using a two sieve method. Larger samples may be processed using a fluidising column, or Trudgill Tower. Detection of any cysts present is achieved by visual examination of the extracts from the sieves.
If PCN cysts are found, the lot concerned cannot be exported or treated as seed. However, further lots from the same crop can be considered for sale, providing they are cleared by further soil testing.
If necessary, consignments from ware crops can be given phytosanitary clearance by a post-harvest field test, taken exactly as the pre-crop soil test, or by a consignment test on soil riddled from harvested tubers.
Results from consignment tests are issued via the agricultural officer from the the local Area Offices who collected the sample.
If you have any technical enquiries about consignment testing for PCN, please contact Jon Pickup.
The Seed Potatoes (Scotland) Regulations 2000 requires that seed stocks derived in Scotland must originate from nuclear stock (in vitro pathogen tested microplants) produced by SASA. This ensures that the starting material is pathogen-free according to a programme of official testing for indigenous and EU-quarantine pathogens.
Nuclear stock can then be maintained by SASA, on behalf of potato breeders and the industry, as part of a collection of over 700 potato varieties or can be issued to approved micropropagation laboratories for maintenance and further multiplication. Microplants can then be grown in a pest free medium in a protected environment to produce mini-tubers (class Pre-basic TC) or can be grown in the field to produce class Pre-basic 1 tubers. Order forms and charges for SASA's micropropagation services can be found on the Nuclear Stock Documents page which also includes a list of those varieties in the collection which are not subject to Plant Breeders' Rights. Access to varieties which are subject to Rights requires the permission of the breeder or his agent.
For queries about nuclear stock, see the contact details on the Contacts - Potato Branch page.
The testing programme in nuclear stock production is outlined below:
ELISA: PMTV, PVX, PVY, PLRV, PVA, PVS, PVM, PVV, Tomato Black Ring Virus and Potato Latent Virus (non-indigenous virus)
Bioassay: a range of indicator plants are also inoculated to check for common and unusual viruses, and possible new strains of existing viruses and other potato pathogens
Indicator plants: Viruses detected
Capsicum annuum: AMV, PVX
Chenopodium amaranticolor: PVX, PVS, PVT,APLV, PMTV, PBRSV, TRV, AMV, AVB-0, TBRV, TMV
Chenopodium murale: PVS, PVT, AVB-0, APLV, PLV, PVM
Chenopodium quinoa: PVX, PVS, APLV, PBRSV, TMV, PVU, AMV, TBRV, TNV, TRV,
Datura metel: PVX, PVY, PVA, PVM
Nicotiana bethamiana: PMTV, PVA, PVV, PVT, PVX, PVY, PYMV, TSWV, TMV
Nicotiana bigelovii: APMV, APLV, WPMV
Nicotiana clevelandii: PVX, PVY, PVA, APMV, APLV, PVV, TRV, TNV, PVM
Nicotiana debneyi: PVX, PVY, PVS, PVM, PVA, PVY, PMTV, PLV
Nicotiana occidentalis-PI: PotL V, PVX, PVY, WPMV
Nicotiana tabacum (cv. White Burley): PVX, PVY, PVA, TSV, TMV, TNV, TRV, TBRV, PBRSV
Dickeya spp. and Pectobacterium spp. - enrichment and semi-selective medium or PCR
SASA advise within the Scottish Government on any issues relating to the export of Scottish potatoes.
Our work covers a wide range of technical and official activities with the overall aim to facilitate the worldwide trade in Scottish potatoes. At the same time we ensure that the Scottish Government meets its international obligations as National Plant Protection Organisation (NPPO).
We are a primary source of advice for both internal and external stakeholders on potato export and related phytosanitary, technical and trade issues.
SASA develops long-term relationships with relevant authorities in importing countries to effect changes in plant health and import policies in these countries and to explore possibilities of co-operation on technical issues.
Export Liason Officer: John Ellicott
Tel: +44(0)131 244 8963
Potato Co-ordination Officer: Craig Douglas
Tel: +44(0)131 244 6346
You can also forward your enquiries to: firstname.lastname@example.org
Inward seed potato missions are organised by SASA and the Potato Council with the aim of influencing import conditions in the visitors' country, improving contacts with foreign officials and impressing the quality benefits from classification, testing, handling and inspection of seed potatoes in Scotland.
Inward missions in 2013:
Inward missions in 2011:
Inward missions in 2010:
Scotland has been exporting seed and ware potatoes around the world for many decades. Data on the volume of trade, export destinations and varieties exported are collected each month from Phytosanitary Certificates issued by the Scottish Government.
The changes in volume of seed potatoes exported from Scotland since 2000 are shown in the chart below.
Export Statistics give a summary of the Scottish potato trade to countries requiring a Phytosanitary Certificate. All figures exclude trade with countries which are currently members of the European Union. However, they include exports to the Canary Islands, which are part of Spain but have a special phytosanitary status within the EU.
The main export destinations for Scottish seed potatoes for season 2011/2012 are reflected in the chart below:
Detailed information on seed or ware potato export volumes, destinations and varieties can be accessed by choosing the corresponding Excel file below:
View and download the Export statistics
Scotland exports seed and ware potatoes to more than 40 different countries around the world. Information on the conditions and phytosanitary requirements for the importation of Scottish potatoes into individual countries outside the EU can be found on the Scottish Government website.
Seed potato store
IMPORT OF SEED AND WARE POTATOES TO SCOTLAND
Please be aware of a new statutory pre-import notification requirements, which will come into force on 9 February 2013, concerning the import of ware potatoes to Scotland from Poland, Portugal, Romania and Spain.
These changes are in addition to the notification requirements already in place for seed potatoes and also ware from Poland. They recognise the plant health situation in these Member States and the potential increase in imports from these regions following the poor UK harvest in 2012.
These new measures will help protect Scotland and the UK's plant health status. Similar arrrangements are already in place in England.
SUMMARY OF IMPORT REQUIREMENTS
|SEED||Poland||Pre-import notification and an official ring rot test certificate|
|All non-Scottish||Pre-import notification and a plant passport/official certificate|
PROHIBITED, except from Switzerland where equivalent measures to those for EU countries are in place
|WARE||Algeria, Egypt, Israel, Libya, Morocco, Syria, Tunisia and Turkey||
If importing directly through a Scottish port contact: email@example.com for information on requirements.
For Egyptian ware notification requirements see below.
Pre-import notification, official ring rot test certificate and a registration number
|WARE||Portugal, Romania and Spain||Pre-import notification and a registration number|
|WARE||Other EU countries and Switzerland||Registration number|
|WARE||Other non-EU countries||PROHIBITED|
At least 48 hours prior to the intended date of introduction into Scotland of the potatoes, the importer must supply the following details to their local RPID Area Office:
Due to high levels of ring rot outbreaks in Poland the Scottish Government is extending the pre-import notification requirement for Poland. Polish seed and ware potatoes must now be accompanied at the time of import into Scotland by a Ring Rot test certificate issued by the Polish Plant Health Authority. Although it will not be a requirement for Polish consignments to be accompanied by the certificate after import, it is important that the certificate is retained following import to demonstrate the compliance with the new requirements.
The Scottish Government is extending the pre-import notification requirement to ware potatoes from above Member States. This is in response to the Epitrix (flea beetle) situation in Portugal and Spain (there was a voluntary notification arrangement already in place) and the number of Ring Rot outbreaks in Romania.
Ware imports are prohibited unless the potatoes are grown in an area recognised by EC as being free from the Brown Rot bacterium Ralstonia solanacearum and are accompanied by a phytosanitary certificate which must comply with detailed plant health conditions. Companies wishing to pack, wash or otherwise process Egyptian potatoes are required to apply to their local RPID Area Office for annual authorisation to handle potatoes from this country (please contact AO for further details). Import of Egyptian ware potatoes are subject to testing for Brown Rot, the fee for this must be paid by the importer.
Further information on the notifications is available on the Scottish Government's Potato Health Controls' page. See also the guide: "Defending your potato crop against disease: a guide for ware growers".
Register of Pre-Basic and Basic Scottish Seed Potato Crops
Register of Seed Potato Producers
Scottish Seed Potato Variety Statistics
For more information on the online Scottish Seed Potato Register, view the poster.
Potato-infecting viruses cause significant damage worldwide and represent a significant threat to seed potato industries. The incidence of virus in seed potatoes can have a significant impact on crop quality (both seed and ware). Virus infection can result in seed crops not meeting the official standard for a class (downgrading) or even for certification as seed potatoes (failure). As the cultivation of potatoes involves vegetative (asexual) reproduction, virus infection in the parent tuber is generally passed on to the next generation. Virus free crops are at risk from transmission of virus from sources of infection outwith the planted crop. The greatest risk is presented by virus infections in neighbouring potato crops, in groundkeepers originating from previous potato crops that have continued to grow in the soil, and from virus reservoirs in the environment, e.g. weeds.
Work carried out at SASA using data from the Scottish Seed Potato Classification Scheme has shown that crops grown from a parent crop in which symptoms of infection had been seen at the previous year’s classification inspections have a far greater likelihood of exhibiting virus symptoms than crops grown from a parent crop in which no virus had been seen during inspection. For example, over the period 2009-2011, whilst virus symptoms were observed in 16% of the crops grown, the virus incidence was 52% for stocks grown from parental material, and 13% for crops grown from parent stock in which no symptoms had been visible. These data indicate a four-fold difference in the likelihood of mosaic being seen in a daughter crop depending upon whether virus had been observed in the parent crop.
The location where crops are grown has an effect on the likelihood of a crop acquiring infection, with the probability increasing when crops are grown in areas where more commercial stocks are in cultivation. The area of ware potato crops is likely to have a more significant effect than the area of seed crops.
Potato viruses are transmitted by a number of vectors. Whilst over 75% of the virus infections seen in Scottish seed potato crops are transmitted by aphids (e.g. Potato Leaf Roll Virus – PLRV, potyviruses such as Potato Viruses Y, A and V), other viruses may be transmitted by nematodes (e.g. Tobacco Rattle Virus - TRV), fungi (Potato Mop Top Virus - PMTV) or be transmitted by physical contact (e.g. Potato Virus X). Under Scottish field conditions the symptoms of virus infection are not usually seen during the growing season in which the transmission takes place.
Aphid transmitted potato viruses may be transmitted in a persistent (e.g. PLRV) or a non-persistent manner (e.g. Potato Viruses Y, A and V). Persistently transmitted potato viruses infect the vector aphid for its lifetime and any plants on which such an aphid then feeds will be at risk of acquiring the virus. Non-persistently transmitted potato viruses can only be transmitted immediately after aphids have fed on an infected plant. Non-colonising aphid species, such as cereal aphids, that do not use potato as a host but alight on potato plants and probe the leaves, can transmit these viruses.
Details of the virus tolerances for classified seed potatoes in Scotland are set out in the SPCS in Scotland leaflet.
The SPCS Aphid Monitoring Programme is suspended for 2014. SASA recommends that growers take advice from their agronomists over their virus management programmes for this season.
The levels of virus present in the 2013 seed crops, which provides the inoculum for virus infection in 2014, were very low. The incidence of crops containing leafroll fell to the lowest level on record in 2013 and the incidence of mosaics was the lowest since 2006. As the aphid vectors that transmit the viruses causing mosaics symptoms were moderately abundant in 2013, mosaics are expected to remain at similar levels as seen last season. Peach-potato aphids that transmit leafroll were relatively scarce last year, so the expectation is for this virus to remain close to the low levels observed in 2013. Following a relatively mild winter, Peach-potato aphids are expected to be more numerous during the early season, so there is a greater risk of leafroll transmission. However, the scarcity of virus inoculum within the planted crop should limit the extent of this risk. It is not currently possible to make long range forecasts of the abundance of the aphid vectors of mosaics. SASA therefore advises growers to consult the SASA website where information on the abundance of aphid vectors based on the catches from a network of suction traps and PCL funded yellow water traps of potato viruses will be regularly updated over the course of the growing season.
An estimate of the likelihood that aphids will transmit non-persistent potato viruses (e.g. PVY) in the field can be made using the data collected by the aphid suction traps. This estimate, the aphid vector pressure, is calculated by summing the total catch of each aphid species, after multiplication by a factor estimating the efficiency of that species as a vector of PVY. Details of the vector efficiencies used in these calculations are available via the Potato Council Aphid Monitoring webpages. The vector pressure is a very coarse measure of the likelihood of virus transmission. Numerous factors will influence virus transmission, including complex interactions between aphid species and the strain of virus they transmit.
The number of aphids known to vector potato viruses that have been caught in the Scottish suction traps during the week prior to 18 August is much lower than in previous weeks and the cumulative total for 2014 is below the average total for the previous 10 years. Following high activity of Leaf-Curling Plum aphids (Brachycaudus helichrysi) and Willow-Carrot aphids (Cavariella aegopodii) in late May and early June, cereal aphids have been predominant since early July.
The cumulative aphid vector pressure for 2014 (up to 18 August) now ranks at 21st over the last 31 years. The species making the greatest contribution to the overall vector pressure to date have been the Bird Cherry-Oat aphid (Rhopalosiphum padi) with 55% and the Rose-Grain aphid (Metopolophium dirhodum) with 29%.
The cumulative aphid vector pressure for 2014 (up to 13 August) now ranks 15th over the last 31 years. All three cereal aphid vectors are now making an important contribution to the overall vector pressure, with the Rose-Grain aphid (Metopolophium dirhodum) responsible for 22% of the total vector pressure, the Bird Cherry-Oat aphid (Rhopalosiphum padi) responsible for a further 38% and the Grain aphid (Sitobion avenae) with 32%.
The cumulative aphid vector pressure for 2014 (up to 18 August) now ranks 11th over the last 29 years. The species making the greatest contribution to the overall vector pressure to date are the Grain aphid (Sitobion avenae) with 40% and the Bird Cherry-Oat aphid (Rhopalosiphum padi) with 32%.
Variety has a very important effect on the incidence of virus symptoms observed at classification inspections. The term ‘varietal propensity’ has been adopted to describe whether symptoms observed within a variety are above or below the average across the whole Scottish seed crop (i.e. Propensity = % of diseased crops of variety /% of diseased crops of all varieties).
The table below summarises varietal propensity information collected over the period 2009-2012 using data on symptom expression at crop inspection (Mosaics and Leafroll) and laboratory virus diagnoses on leaf samples submitted to SASA from plants exhibiting virus symptoms during crop inspections (PVYN, PVYO/C, PVA and PVV). Values greater than 1 indicate that a virus/symptom is more likely to be found in that variety and values less than 1 indicate that it is less likely to be found in that variety. The table shows values which are significantly greater than 1 at the p<0.01 level shaded in red; values which are significantly greater than 1 at just the p<0.05 level shaded in orange; values which are significantly less than 1 at the p<0.01 level shaded in dark green; and values which are significantly less than 1 at just the p<0.05 level shaded in light green. Values that are not significantly different from 1 at the 0.05 level are left clear. Sample size has a marked effect on the likelihood of significant departures from 1, both for varieties where few crops have been inspected and for viruses/symptoms where the incidence is low (e.g. PVA, PVV, Leafroll).
Propensity values can be used to rank varieties in relation to any particular virus/symptom. However, they should not be used to make quantitative comparisons between viruses/symptoms. As the reliability of propensity data depends upon the inspection and sampling of an extensive number of crops, it is less reliable for varieties with relatively few crops which are only grown over a relatively small area e.g., new varieties. For these reasons, propensity data are only presented for varieties with over 100 crops grown over 2009-2012.
Varietal resistance scores, e.g. those provided on the British Potato Variety database, relate to resistance to PVYO/C whereas propensity values generally relate to the strains of viruses that are present in the field (e.g. the PVYEU-NTN serotype of PVYN is the dominant virus within the Scottish classification scheme). Therefore, there may not be a straightforward relationship between the two values.
Consideration of varietal propensity should be an important part of any virus management programme. Whether a variety has a propensity to leafroll or to PVY can be used to determine the appropriate means of protecting the crop through a control programme for the appropriate aphid vector species. Propensity should also be considered in any planting programme as there will be advantages in ensuring that varieties with a propensity to say, PVY, are planted away from crops which are considered a likely source of inoculum for that virus.
In order to protect the overall health of all potatoes grown in Scotland ware potato production must meet minimum quality standard monitored and verified by the Scottish Government.
Scotland is a “Community Grade Region” for seed potatoes. This status requires that all potatoes planted in Scotland must be Basic category seed.
Pre-basic or Basic category seed (Scottish classes PB, SE, E or A). Seed bought in from the EU member states must carry a community grade on the label (EC1, EC2 or EC3) in addition to the category and class information.
Ware growers are permitted to plant farm saved seed from classified seed but this seed may only be grown for one generation ie to produce the final ware crop.
The community grade region status also requires that all crops grown should meet the Basic seed progeny tolerance for virus of 4%. Any potato crops grown in Scotland (seed or ware) with virus levels above 4% may be subject to compulsory destination, however the vast majority of crops contain little or no virus.
Ware growers must notify the Scottish Government of all potato crops planted in Scotland. SASA issues the notification forms (PP1) and collates and retains the returns. This information is required to allow swift and co-ordinated action in the event of a plant health outbreak and to underpin the other potato plant health measures in Scotland.
For further information see the Ware Potatoes documents page.
Potato Branch address: Potato Branch, SASA, Roddinglaw Road, Edinburgh, EH12 9FJ
Head of Potato Branch
Pathology Manager: Dr R (Ros) McHugh
Tel: +44(0)131 244 8921
Potato Export Liaison Officer: Mr J (John) Ellicott
Tel: +44(0)131 244 8963
Nuclear Stock Manager: Miss S (Sandra) Goodfellow
Tel: +44(0)131 244 8852
Seed Potato Classification Scheme (SPCS)
Address: Seed Potato Classification Scheme Section, SASA, Roddinglaw Road, Edinburgh, EH12 9FJ
Fax: +44(0)131 244 8920 | Email: firstname.lastname@example.org
Seed Potato Classification Scheme Technical Manager: Mr J (John) Ellicott
Tel: +44(0)131 244 8963
Growing Crop Certification Manager: Ms M (Maureen) McCreath
Tel: +44(0)131 244 8818
For all enquiries regarding Growing Crop Inspections, PCN and Marketing please contact the Scheme Officers below
Scheme Officer: Mrs W (Wilma) Sloan
Tel: +44(0)131 244 6349
Scheme Officer: Mr S (Stephen) Fotheringham
Tel: +44(0)131 244 6348
Scheme Administrator: Mrs C (Christine) Weir
Tel: +44(0)131 244 6350
In 2012 Edinburgh was the venue for the World Potato Congress hosted by the Potato Council. Find out more about the congress, including the programme, social activities and industry interaction at the World Potato Congress website.
Dr John Kerr from SASA spoke on the topic “Keeping it Clean … and proving it”. In the presentation John discussed the essential role of Classified Seed has to play in a robust and sustainable supply chain. His talk showcased the Scottish Seed Potato classification scheme as an exemplar. He went on to highlight the need for a harmonised global approach to measuring seed quality, discussing how the UNECE Standard on Seed Potatoes can be used to improve trading relations and give farmers, wherever they are growing potatoes, access to good quality seed.
SASA was one of the venues for several of the industry interaction tours on the Wednesday of the programme, giving delegates the chance to see at first hand the wide range of work undertaken by SASA in support of the potato industry.