Viruses that Infect Domesticated Potatoes

This is an overview of viruses that infect the potato (Solanum tuberosum). This article is targeted at the advanced amateur, particularly if you are considering doing some testing of your collection. Most articles about potato viruses focus on just a few of the most common ones. This article lists every virus that I am aware of that is known to infect potato naturally, without human intervention.

Viruses in Collections

Potato collectors should have increased awareness of potato viruses, beyond those that are common in the commercial crop.  Collectors have unique exposure to viruses for a variety of reasons.  Many collectors grow varieties that have been maintained as clones for decades without any virus cleanup.  These varieties may carry viruses that have been extirpated in the commercial crop.  Viruses like Potato Spindle Tuber Viroid, Potato Aucuba Virus, and Potato Latent Virus have been detected in private collections in recent years even though they have been out of the commercial crop for a long time.  Collections also often contain varieties that escaped quarantine.  Anyone who has spent much time in social media knows that people routinely carry potatoes across borders.  Once they are here and have changed hands, there is no way for you to know if they came in through quarantine or in somebody’s backpack.  There must literally be hundreds of such varieties floating around out there.  And it isn’t just potatoes – some of these viruses move in tomatoes and other Solanums, the Andean root and tuber crops, or even further afield, from crops like beets and beans.  Some move in and out of weeds.

I suspect that there are a lot more exotic viruses floating around in collections than anyone realizes.  Collections are rarely tested.  Even when they are tested, they are mostly tested for things that are common, because testing is expensive.  Exotic viruses probably don’t become a problem because private collections are downstream from commercial cultivation and the commercial crop is grown almost entirely from certified seed.  That doesn’t mean that system is fool-proof though, so it is a good idea to test for and eradicate exotic viruses whenever possible.

Eliminating Viruses Through True Seed

It is commonly believed that growing plants from true seed (TPS) is a guaranteed way to eliminate viruses.  That’s not really true.  It is largely true if your exposure is limited to viruses that are common in North America.  The really common potato viruses – Potato Leafroll Virus, Potato Mop Top Virus, Potato Virus A, M, S, X, and Y, and Tobacco Rattle Virus – are not transmitted through true seed.  Exotic viruses may be.  The most common example is Potato Spindle Tuber Viroid, which spreads easily through true seed.

Heat treatment of TPS reduces the odds of transmission of baterial and fungal pathogens, but does little to eliminate viruses if they are carried in the seed.  The incidence of some viruses can be reduced by holding seeds at high temperatures for long periods of time, but this is usually associated with a major reduction in germination.

Virus Commentaries

Commentaries about the viruses are my own and I am not a plant pathologist, so you certainly shouldn’t consider them authoritative.  I probably have done more testing of potatoes from private collections than many professionals though, so I have a different perspective.  I have seen things that don’t always agree with the literature.

Virus Genus Present in North America Frequency in Potato (USA)
Seed Transmitted in Potato
Alfalfa Mosaic Virus (AMV) Alfamovirus Yes Uncommon Possibly
Andean Latent Virus (APLV) / Eggplant Mosaic Virus (EMV) Tymovirus Yes Never? Possibly
Andean Potato Mottle Virus (APMoV) Comovirus No Never No
Arracacha Virus B (AVB) Cheravirus Unknown Never? Yes
Beet Curly Top Virus (BCTV) Curtovirus Yes Rare No
Cucumber Mosaic Virus (CMV) Cucumovirus Yes Rare Possibly
Eggplant Mottled Dwarf Virus (EMDV) Nucleorhabdovirus No Never No
Impatiens Necrotic Spot Virus (INSV) Tospovirus Yes Rare Possibly
Pepino Mosaic Virus (PepMV) Potexvirus Yes Never? Probably not
Potato Aucuba Mosaic Virus (PAMV) Potexvirus Yes Rare No
Potato Black Ringspot Virus (PBRSV) Nepovirus No Never No
Potato Latent Virus (PotLV) Carlavirus Yes Rare Probably not
Potato Leafroll Virus (PLRV) Polerovirus Yes Common No
Potato Necrosis Virus (PoNV) Alphanecrovirus No Never Unknown
Potato Mop Top Virus (PMTV) Pomovirus Yes Common No
Potato Rough Dwarf Virus (PRDV) Carlavirus No Never Unknown
Potato Spindle Tuber Viroid (PSTVd) Pospiviroid Yes Rare Yes
Potato Virus A (PVA) Potyvirus Yes Common No
Potato Virus H (PVH) Carlavirus No Never Unknown
Potato Virus M (PVM) Carlavirus Yes Uncommon No
Potato Virus P (PVP) Carlavirus No Never Unknown
Potato Virus S (PVS) Carlavirus Yes Common No
Potato Virus T (PVT) Tepovirus No Never Probably
Potato Virus U (PVU) Nepovirus No Never Unknown
Potato Virus V (PVV) Potyvirus No Never No
Potato Virus X (PVX) Potexvirus Yes Common No
Potato Virus Y (PVY) Potyvirus Yes Common No
Potato Yellow Blotch Virus (PYBV) Potyvirus No Never Unknown
Potato Yellow Dwarf Virus (PYDV) Nucleorhabdovirus Yes Rare No
Potato Yellow Mosaic Virus (PYMV) Begomovirus No Never Unknown
Potato Yellow Vein Virus (PYVV) Crinivirus No Never Unknown
Potato Yellowing Virus (PYV) Ilarvirus Unknown Unknown Yes
Solanum Apical Leaf Curling Virus (SALCV) Begomovirus No Never Unknown
Sowbane Mosaic Virus (SoMV) Sobemovirus Yes Rare Possibly
Tobacco Rattle Virus (TRV) Tobravirus Yes Uncommon Probably not
Tobacco Mosaic Virus (TMV) Tobamovirus Yes Common No
Tobacco Necrosis Virus (TNV) Necrovirus Yes Rare No
Tobacco Ringspot Virus (TRSV) Nepovirus Yes Rare Possibly
Tobacco Streak Virus (TSV) Ilarvirus Yes Rare Possibly
Tomato Leaf Curl New Dehli Virus (ToLCNDV) Begomovirus No Never Unknown
Tomato Mosaic Virus (TMoV) Tobamovirus Yes Rare No
Tomato Spotted Wilt Virus (TSWV) Tospovirus Yes Uncommon Probably not
Tomato Yellow Leaf Curl Virus (TYLCV) Begomovirus Yes Unknown No
Tomato Yellow Mosaic Virus (ToYMV) Begomovirus No Never Unknown
Tomato Yellow Vein Streak Virus (ToYVSV) / Potato Deforming Mosaic Virus (PDMV) Begomovirus No Never Unknown
Wild Potato Mosaic Virus (WPMV) Potyvirus No Never Probably not

Alfalfa Mosaic Virus

Not a common virus in potatoes from what I can tell.  It is one of those that turns up from time to time in well-traveled potatoes.  Black Irish and Peruanita both tested positive here for AMV.  A small amount of transmission though seed has been observed in some potato relatives, so it is possible that this virus could infect TPS.

Andean Potato Latent Virus

This virus is present in some heirloom ulluco varieties, which is the main reason why I no longer grow them.  We test every known host here for APLV and have never seen it in a potato or in anything other than those ulluco varieties, so I don’t think it spreads easily, but it is possible that it could spread through TPS.  This is a very good reason not to grow the old ullucos or to keep them absolutely isolated from potatoes if you insist on it.

Andean Potato Mosaic Virus

Probably not present in the USA or at least very rare if so.

Arracacha Virus B

I have never seen this virus, but it is among those that worry me the most.  It infects several Andean tuber crops and is also capable of infecting potatoes.  It is somewhat common in oca in the Andes and the oca strain can infect potatoes and is known to spread through TPS.

Beet Curly Top Virus

I have never seen a positive test for this virus, but it is fairly common in other hosts and occasionally makes it to potato.  Spread primarily by leafhoppers.  The symptoms may appear similar to herbicide poisoning.

Cucumber Mosaic Virus

An extremely common virus that is not common in potatoes.  I have only seen it once, in the variety ‘Raudar Islenskar’.  It is rare enough that I no longer routinely test for CMV.

Eggplant Mottled Dwarf Virus

 

Inpatiens Necrotic Spot Virus

 

Potato Aucuba Mosaic Virus

 

Potato Black Ringspot Virus

 

Potato Latent Virus

 

Potato Leafroll Virus

 

Potato Necrosis Virus

 

Potato Mop-top Virus

 

Potato Rough Dwarf Virus

 

Potato Spindle Tuber Viroid

This is probably the top concern of regulators and so it should be one of your top concerns as well.  You don’t want to be the person who finds out the hard way that PSTVd is present in your collection.  This viroid spreads easily and infects true seed.  It has a number of alternative hosts and so could become established easily.  It has been present in North America for a long time, but appears to have been eliminated from the commercial crop.  It occasionally turns up in collections and breeding programs.  The latter may indicate that there are still some infected seeds in gene banks.  Unfortunately, it requires expensive nucleic acid hybdridization testing to detect, so most people are not going to be able to afford to test for this routinely.  Be on the lookout for the characteristic change in tuber shape to more of a football shaped tuber (unless the variety already has that shape, in which case you’re out of luck).

Potato Virus A

PVA is a very common mosaic virus that may be asymptomatic, particularly in mild climates.  I have seen it often in heirloom varieties and even certified seed tubers and test for it routinely.

Potato Virus H

 

Potato Virus M

PVM is said to be a very common potato virus, but I have only seen it once.  It is a mosaic virus that may be asymptomatic, particularly in mild climates.

Potato Virus P

 

Potato Virus S

PVS is a very common mosaic virus that may be asymptomatic, particularly in mild climates.  I have seen it often in heirloom varieties and even certified seed tubers and test for it routinely.  I also got a positive test in ad hoc tubers supplied by the USDA potato introduction station.

Potato Virus T

I have never seen this virus, but it is among those that worry me the most.  It infects several Andean tuber crops and is also capable of infecting potatoes.  It is somewhat common in oca in the Andes and is known to spread through TPS.

Potato Virus U

Potato Virus V

Potato Virus X

PVX is probably the most common virus infecting uncertified heirloom varieties in the USA.  It can be asymptomatic, particularly in mild climates and when it is the only virus present.  In combination with other viruses, the symptoms can become severe.  I have seen it often in heirloom varieties and even certified seed tubers and test for it routinely.

Potato Virus Y

PVY is probably the most serious of the common potato viruses in the United States, although you could make a case for Potato Leafroll Virus as well.  It spreads easily by aphid and it is common in heirloom varieties and even relatively common in certified seed potatoes.  There are necrotic strains that are even more damaging.  If you test for nothing else, you should test for PVY.  There are immunogical tests for the potyvirus group, which includes PVY, but also PVA and some lesser viruses, so that is the best approach if you don’t need to ID the specific potyvirus.  Happily, PVY does not spread through true seed.

Potato Yellow Blotch Virus

 

Potato Yellow Dwarf Virus

 

Potato Yellow Mosaic Virus

 

Potato Yellow Vein Virus

 

Potato Yellowing Virus

This is on my list of most serious concerns as it is a relatively unknown potato virus that may be present in some yacon varieties.

Solanum Apical Leaf Curl Virus

 

Sowbane Mosaic Virus

 

Tobacco Mosaic Virus

 

Tobacco Rattle Virus

 

Tobacco Necrosis Virus

 

Tobacco Ringspot Virus

 

Tobacco Streak Virus

 

Tomato Leaf Curl New Dehli Virus

 

Tomato Mosaic Virus

 

Tomato Spotted Wilt Virus

 

Tomato Yellow Leaf Curl Virus

 

Tomato Yellow Mosaic Virus

 

Tomato Yellow Vein Streak Virus

 

Wild Potato Mosaic Virus