> What are the best / most affordable places to get virus testing? The most affordable is usually your nearest land grant university, if they have a plant pathology department. Many of them offer testing at cost. Otherwise, you either need to deal with a private lab or do your own testing. Agdia is a private lab that both does testing and sells test supplies. > Can we give a list of which viruses a grower should test for? You would need to put together recommendations at probably no greater level than genus. There are some viruses, like Cucumber Mosaic Virus, that have a very wide host range, but most are more specific. I have a list of dahlia viruses here, if you want to see what that looks like: https://cultivariable.com/instructions/root-crops/… > Can we also compile info on treatments for viruses? Most plants are treated for viruses with a combination of meristem tip culture, thermotherapy (heat), cryotherapy (cold), and chemotherapy (antivirals). It is rare that any one of these does the job and meristem culture is probably the most essential part. That is requires a bit of investment in tools and skills, but is certainly something amateurs can manage if they are serious. There are some viruses that are particularly vulnerable and that can be treated without meristem excision, but they are the exceptions. For example, potato leafroll virus can be treated with a fair degree of success just by heating potato tubers to 38C for a month. Most viruses will not succumb in a tuber though. Long term cold storage can also kill some viruses. Keeping a bulb or tuber in the dark, close to freezing, for two years can kill some viruses or at least significantly reduce virus burden if the plant can survive it. But, for the most part, you need to establish plants in tissue culture with good meristem technique and then subject the cultures to a combination of therapies. At the end of that, you still will probably not have 100% success and will need to test plants grown from each culture to determine which are still infected. > I ask about virus treatment because it seems to me that there's an increasing amount of literature saying that some plant viruses can be spread through seeds. Many viruses transmit through seeds or pollen. Those that are considered serious threats to agriculture have usually been kept isolated, but outside of crop plants, there are many. Seed can be used to produce clean plants a lot of the time, but it totally depends on what the parent is infected with. As to your other questions: * There are several different methods of virus testing: immunological, PCR, and high throughput sequencing (and some lesser ones like nucleic acid hybridization which must be done for some viroids). Immunological tests don't require much skill and you can potentially do your own. There are immunological strip tests for some more common viruses that work basically like a consumer pregnancy test and are intended for end users. You just grind up some leaf material, dip the stick, and wait. I think these typically work out to about $5-$10 per sample. The next step up is ELISA. This requires a bit more skill and equipment, but is still something that you can certainly manage if you can follow a recipe to bake a cake. The minimum purchase is going to be several hundred dollars, but the cost per sample is probably closer to $1 to $2. So, if you have a lot of plants to test or can group together with others, doing your own ELISA is almost always the cheapest option. The next step up is PCR, which can be used to test a much wider range of viruses and, importantly, virus genera. Very few people will be able to manage PCR at home and it is fairly pricey to get it done privately (somewhere in the vicinity of $100/sample), but it is the only option for many viruses that are less common. The final option, which is just starting to become more common is HTS, where they sequence everything and then look for matches to viral sequences. This is probably still too expensive for amateurs, but it probably won't be too long before you can send off a sample and get a complete list of viruses, which will certainly simplify things. * You would have to study the literature for each species to get a list of viruses that infect it. For more common plants, you may find that labs already have done the research and offer a recommended panel of tests. * I'm not an expert, but I don't think there are more seed transmitted viruses. I think there was generally poor understanding, particularly among amateurs, that they existed. I also think that increased testing keeps revealing viruses where nobody expected them. The more that you test, the more that you find, and testing is getting cheaper and more comprehensive all the time. * To try bulb/tuber thermotherapy, you would first want to know what virus(es) is present and then look for existing research to see if that virus is particularly heat sensitive. Unless it is exceptionally sensitive, treating the whole organ is probably not going to succeed. Cheers! Bill On Sun, Nov 10, 2019 at 10:50 AM <michaelcmace@gmail.com> wrote: > Ahhhh, viruses again. > > I want to make a comment, but let me start this by saying that I am not > about to criticize ANYONE on the list, or anything that was just posted. > It's all good stuff, and we are all trying to help. But I want to talk > about > a pattern we've all fallen into and see if we can improve it. > > Here's what tends to happen when the the subject of viruses comes up on the > list: > --Somebody posts a picture of an affected leaf > --Someone says it looks infected > --Someone says it looks like environmental or insect damage > --Someone then suggests that the grower get a virus test > --Someone suggests that the grower destroy those plants > --Someone suggests that the grower share only seeds > > The grower is left frightened and unsure about what to do. > > Rinse and repeat a year later. > > I think we can do a little better. First, Nhu and Jacob and other PBS > members compiled a very extensive page on the wiki about bulb-related > viruses, leaf pictures, and what to do. The link is below, and anytime the > subject comes up we should remind folks that it's there: > > https://pacificbulbsociety.org/pbswiki/index.php/… > > However, even with that guide, it's still pretty hard be sure if you have > viruses and what to do about them. It's especially difficult because > (according to what I've read) leaf damage from stress really can look a lot > like virus damage, and some viruses in some conditions won't do any leaf > damage at all. So you can't ever really be sure. > > I'd like to ask if we list members could collect some more info to add to > the wiki page: > > --What are the best / most affordable places to get virus testing? We have > a > directory of seed suppliers; how about an informal directory of virus > testing suppliers? If people want to post links to the testing services > they > use, I'd be glad to put that in the wiki. > > --Can we give a list of which viruses a grower should test for? The wiki > page lists a bewildering array of viruses, and when I looked for virus > tests > online, they all seem to charge per virus. So you have to ask specifically > which virus you want to test for. I don't know about you, but I would not > have a clue what to test for if I had a questionable leaf. Could we compile > a table that cross references genera and the viruses to test for? I'd be > glad to help build that if folks on the list can provide the info. > > --Can we also compile info on treatments for viruses? There's some > literature online that talks about commercial heat treatment for bulbs and > corms that have viruses (it's apparently done for some commercial genera > like Freesia). Supposedly there is a magic temperature range where you can > get them hot enough to inactivate the virus but not hot enough to kill the > bulb. You might think there's no way an amateur grower could do something > precise like that, but actually if you have a sous vide cooker, it's now > very easy to hold something at an exact temperature for hours or even a > day. > It would be great to know if that could work for bulbs or seeds. > > --I ask about virus treatment because it seems to me that there's an > increasing amount of literature saying that some plant viruses can be > spread > through seeds. For example, it's just been made illegal to import pepper > and > tomato seeds into the US without a phyto, due to viruses in seeds. We all > tend to treat seed propagation as the magic firewall that will prevent > viruses from spreading from grower to grower. If we suddenly discovered > that > the firewall leaks more than we thought, we could end up with import > restrictions or even rules against sharing seeds within a country. If we > get > ahead of that issue, we'll all be more worry-free in the future. > > So my questions to the list are: > > --If you've ever done virus testing, which service(s) did you use and what > did it cost? > > --Can anyone give information on which viruses are most common for a > particular genus, or suggestions on how to know which viruses we should > test > for if we suspect we have an infection? (That info is most important for > amaryllids, since they get asked about the most often on the list.) > > --Does anyone with more botanical knowledge than me know if there really is > an increase in reports of seed-transmitted viruses? Should we be worrying > about that? (It's easy to scare yourself from the info online, as is true > of > any disease-related info on the web.) > > --Does anyone have knowledge of heat treatment (or other treatments) for > plant viruses? I'd be willing to do some experiments with a sous vide > cooker > to see if I could heat-treat seeds or bulbs without killing them, but I > need > to know the temperature and number of hours required. > > Any thoughts? > > Thanks, > > Mike > > _______________________________________________ > pbs mailing list > pbs@lists.pacificbulbsociety.net > http://lists.pacificbulbsociety.net/cgi-bin/… > _______________________________________________ pbs mailing list pbs@lists.pacificbulbsociety.net http://lists.pacificbulbsociety.net/cgi-bin/…