PNWGal KitCMC so is it possible that plants testing positive for DMV or DCMV could actually have EPRV/EPRS?
That should not be the case with the WSU tests, nor with the recently developed Agdia tests. They have been specifically developed to not react to the DMV-EPRS. Who knows what the Utah tests are catching.
USU recently published a dahlia fact sheet that references this USU page dated August 2022 that stated "In Utah, the most prevalent strain is DMV-D10". Also of note because I am/was really hoping to identify virus resistant varieties: "There are no resistant dahlia varieties and plants cannot be cured once infected." Sorry for that detour.
The USU research seemed to conflict with what I had heard from Agdia and Dr. Pappu, so I asked them about it and also referenced another paper from August 2022 proposing that DMV and DCMV are the same virus, and repeating that DMV-D10 is a non-infectious strain embedded in dahlia DNA and lacking a mechanism for infection.
The USU response from Dr. Melanie Stock:
"thanks for sharing the paper. It is important to note that the research is ongoing - so much we do not know and are learning. The endogenous pararetroviruses (D-10) still causes symptoms in some dahlias without the presence of another virus - this is research we are working on at USU and have documented in our dahlia surveys in the state (the mosaic pattern looks different in dahlia with only D10 - it is mottling of light green and dark green vs the more intense yellow and green mottling associated with the holland strain; effects on yield are unknown). It is also fairly common to find dahlia without D10 - 37% of plants in one survey year didn't have it. EPRVs have also been reported to be activated by stress factors such as temperature, plant age, tissue culture etc (https://www.frontiersin.org/articles/10.3389/fpls.2021.689307/full#B44). One thing to note is the Geering paper is a molecular biology study, so their methods are running and analyzing the DNA components. They are not doing inoculation experiments. They wrote it is "unlikely" to be infectious - not that it isn't. This is based on what they did not find in the DNA - but they didn't physically try to inoculate. Because a specific protein is missing, they can conclude aphids do not transmit it and they do not. Other viruses, however, have been found without a zinc finger motif and are infectious - that D10 doesn't have this does not mean it is not infectious - there is just so much research needed to understand the different ways viruses infect. For example, possible transmission could be with a knife - the research just isn't there yet. From Dr. Nischwitz's work at USU though, we know that D10 is not in all plants and when it is found alone in a plant (no other virus), we do see symptoms - but the effect on yield is unknown, or the impact of stress factors. If you'd like to discuss more, please email us, particularly Claudia Nischwitz, my plant pathologist colleague. Thank you so much for your interest!"
