Cleanup of Virus Infected Clonal Varieties

Note: I have updated these prices a few times because there were errors in the spreadsheet that I used to calculate them.  The good news is that they are lower.

I am planning my next submission of samples for PCR testing in July, so if you want to start cleanup on a variety this year, I would need to receive it by the second week of April to have it ready in time.

Because I am now regularly cleaning varieties in tissue culture and virus testing them, I can extend this service to others.  Normally, I do this by invitation, but if I have invited you, you are welcome to share the info with others who you think could use it.  This is a hidden page that does not show up on the site and can only be accessed by the link.  Please don’t post it anywhere with wide distribution, as I am not seeking to become a full time lab.  I don’t make much money at this, but it does help to offset some of the material costs for my own testing work.  Currently, I can clean up potato, oca, ulluco, mashua, yacon, sunchoke, dahlia, and arracacha.  I could probably also manage sweet potato, but I haven’t tried it yet so the set up costs might be a little higher.

The bottom line is that it costs $250 for a hobbyist level cleanup that only uses ELISA tests for diseases that are common in the USA and a minimum of $650 for a cleanup that uses PCR tests performed by a professional lab.  Read on to learn about the differences.  Once your varieties are clean, I can also keep them in storage for $50/year and provide clean plantlets on demand.

I need enough starting material to get about 10 sprouts, which is one medium tuber for most of these plants, except for yacon, dahlia, and arracacha, for which I need at least three sproutable portions.  If you have plenty, send me three tubers, which will give me some backup to work with if a culture gets contaminated or something else goes wrong.  I prefer to start from tubers because the sprouts are easier to work with, but I can also use a small plant if the timing is wrong for tubers.  I can only accept samples from within the USA.

It is possible, though rare, that I might never be successful in cleaning up a variety, in which case you will be out the testing costs.  So far, I have cleaned up more than 80 varieties and only 1 has eluded me.

The process usually takes between six months and two years (rarely, it could be even longer), depending on things like how dormant the samples that you send me are, when I am next sending out a batch of samples for PCR, and how many attempts it takes for me to get the variety clean.  I will return three clean tissue culture plantlets, or as many as you want (within reason) for an additional $5/plantlet.

My cleanup process involves the following steps:

  • Blind cleanup
  • On-site virus testing
  • Comprehensive virus/viroid testing


Blind cleanup means that I don’t test varieties before starting the process.  I have learned from experience that every variety I test is infected with something, so this is a waste of money.  Instead, I proceed directly to meristem culture.  Tubers are sprouted, then I excise several meristems and culture them on ribavirin medium at high temperature.  Any surviving plantlets are then subcultured on growth medium and, when of appropriate size, virus tested.  This process is repeated as many times as necessary to get negative results on all tests.  On average, it takes three rounds of culturing and testing.  Blind cleanup costs $150.

On-site Testing

The next phase is ELISA virus testing, which I perform here.  I test for viruses that are known to be common in the USA or that I have seen before.  The exact mix varies by species.  For potato, it is Alfalfa Mosaic Virus, Potato Leafroll Virus, Potato Viruses M, S, X, and the Potyvirus group, which includes a number of potato infecting viruses such as Potato Virus A, V, and Y.  If you know that you have another disease in your area, I can probably acquire an ELISA test for it, but we’ll have to discuss the costs.  On-site testing costs $100, no matter how many tries it takes me to complete the cleanup.  I do not guarantee these results.  ELISA is not perfect and neither am I.  Every once in a while, a plant that tested clean in ELISA tests positive under the more sensitive PCR test.  In my own work, the on-site testing is performed only to ensure that I don’t send a variety off for PCR while it is still infected with something common.  For most hobbyists, ELISA should be sufficient, but if you are trying to establish foundation stock for sale, then I really recommend getting comprehensive testing.  Heirloom varieties of Andean tuber crops other than the potato should always undergo comprehensive testing since there are viruses that are common in these crops for which no ELISA test is available.  But, the good news is, if you have varieties of these crops that I don’t have, I’ll be happy to pick up the testing cost if I can keep the variety and add it to the collection.

Spindle Tuber Viroid

For potatoes, even if you don’t want comprehensive testing, you might want to add one lab test for Potato Spindle Tuber Viroid.  I cannot test for this on-site.  I have never seen a positive result for this, but it is considered to be endemic in the USA and infects true seed, so it could be really nasty to have in your collection.  I can get a PSTVd test for $100/sample.  If you want to do 5 samples or more, I can bring the cost down by 20% or more.  If the test comes back positive, I will have to attempt cleanup again and you will need to pay for another round of testing.  I have no idea how difficult cleanup might be, since I have never seen this, but the literature indicates that it is possible.

Comprehensive Testing

For most people, the on-site virus testing will probably be sufficient.  In my experience, it will result in totally clean varieties in about 19/20 cases.  If you are worried that you might be dealing with an unusual or exotic virus, then you might want comprehensive testing.  If you suspect that a variety might have been imported, let’s say informally, from outside the country, you really should get the full set of tests.  I do not perform this testing, but send samples to a professional lab for PCR tests on all 18 virus families that are known to infect the clonally propagated crops that we grow.  This is expensive, costing about $400, but it will find anything that the variety is infected with.  If you have particular suspicions, it is possible to reduce this cost by narrowing down the number of virus groups that you want to test for.  If a test comes back positive, then I will need to retry cleanup and test again, although the next time we can test only for the virus groups that were previously detected.  The full lab test results will be passed on to you.

Culture Storage/Maintenance

I can also offer ongoing storage of your clean cultures.  If your variety is interesting to me and you will allow me to list it in the catalog, I will store it for free as long as I list it.  If you bred it, I will also pay you a royalty on sales.  If you want to keep it private, then I will store it for $50 year.  If you ever need more clean plantlets, then you just pay $5/ea plus shipping.