I grow ulluco tubers from tissue culture plantlets that have been tested for the following viruses.  Beginning in 2022, I am offering plantlets instead of tubers for the most part, so I am ending field testing.  My master tissue culture plantlets are tested once and then all future propagation is assumed to be clean.  The master plantlets have passed through multiple rounds of virus chemotherapy in the hope that any unreported viruses that might infect ulluco have also been cleared.

Virus	Method	Rationale
Andean Potato Latent Virus (APLV)	ELISA	Some heirloom ullucos have tested positive for APLV in the past.  I don’t do ongoing testing because I have never seen a field positive.
Comovirus genus	PCR	I suspect the presence of Ulluco Virus C in some heirloom ullucos.  I don’t do ongoing testing because we have never seen a field positive.
Papaya Mosaic Virus (PapMV)	Immunostrip & ELISA	Many heirloom ullucos are positive for PapMV.  I have not seen a positive result for years, but it is easy to test for, so better safe than sorry.
Potato Leafroll Virus (PLRV)	ELISA	Some heirloom ullucos are infected with PLRV or a closely related virus.
Potato Virus T (PVT)	ELISA	PVT is present in many Andean root crops in the Andes, but I have never seen a positive result.  I will probably stop testing for this virus in seed-grown ullucos after 2020.
Potyvirus genus	Immunostrip & ELISA	Primarily screening for Ulluco Mosaic Virus, which has probably been detected in heirloom ulluco varieties in the past.  Because potyvirus is also a group that widely infects Andean tubers, I test everything annually.
Tobamovirus genus	PCR	Screening for Ulluco Mild Mosaic Virus.  An unidentified tombamovirus was once detected in an heirloom ulluco, which was most likely UMMV.  I will probably stop testing for this virus in seed-grown ullucos after 2020.