How to Save Virus-Infected Varieties; Thermotherapy for Crops

Hello there, and welcome back to Hydroponics Daily, your go-to podcast for everything soilless cultivation. I am your host, Dr. Russell Sharp, the founder of Eutrema Limited, a company that makes truly unique fertilizers, biostimulants, and biopesticides that you won't find anywhere else. The technology is completely unique. And today, the topic of the podcast is what I would do if I was faced with a virus in my crop. Specifically a crop where you want to protect the genetic material and you can't just throw the plants away often when we say when you've got a virus the first thing you should do is just destroy all plant material but what if you've got a strain a variety a cultivar that only you've got or is protected or is endangered or you need it for a breeding program or something like that and you need to get rid of the virus what are you going to do you can't give plants tamiflu that technology is not available you can't just wait for their immune system to fight the virus off because they don't have immune systems and so there's only really one option that i'm aware of and that's heat treatment so you when you're planting out cuttings tubers bulbs or seeds immersing them in hot water for a defined period can help with virus control. So we're talking about temperatures of 45 to 55 degrees Celsius. So you wouldn't keep plants, not many plants would live at that sort of temperature, they would soon die off, especially unless the humidity was really, really high. But the duration of which you give this treatment is only like 10 to 60 minutes. So in crops that's regularly, perennial crops, herbaceous perennial crops where they regularly suffer from viruses like sugar cane, sweet potato, banana, even grape vines and some ornamentals, you can do this and with success and control viruses. And you're best obviously doing it with smaller plants because smaller the plants, the more effective the treatment will be because of just the temperature profiles and things like that. Now obviously there's a big challenge there it could be phytotoxic it could just kill your plants from the heat but with a bit of experimentation you could find what is the sweet spot for your particular plant and in fact if I was going to do this if I had a plant that I needed to control the viruses I would do it until the plant breaks so I would get maybe 100 cuttings from a virus infected plant and I'd treat 10 at. What did I say the temperature was, 45 degrees Celsius for 10 minutes, and then all the way up to 10 that would be treated at 55 degrees Celsius for 60 minutes. No idea what that is in Fahrenheit, apologies for American listeners, but it's pretty warm, it's sort of like steam room temperature. So I would do a range and find out at what point did the plants die, and just go slightly below that, and really really stress it, because you don't want any virus particles in that new plant because it will be a source of infection and you will not get a chance to do this twice really so obviously seeds is the easiest but very rarely you won't go on to do that it's after that tubers something dormant a bulb they're going to be much more resistant much more tolerant of those high temperatures whereas a cutting is probably going to be the most sensitive but i would do it until it breaks if you're prepared to lose a few cuttings you could do it on unrooted cuttings and rooted cuttings i'd probably start with rooted cuttings see if you could get away with it because, severely stressing a cutting that's not rooted and then trying to get it to root you know you're not you you're in for a bad case there because you really struggle because it's all the cells are going to be weak and stressed from that heat treatment so i do it on rooted cuttings, newly rooted cuttings, not too much growing media around them. Okay, so that would be my. My suggestion, what are the success rates? If you're doing it on seeds, the sort of typical virus elimination you can achieve is 60 to 90%. Whole plant cure rate, typically around 50%. So you may need to screen the plants and quarantine and destroy any plants that are not completely successful. Micropropagation as well. There's often a technique that's used in micropropagation because you can, these plants are so much smaller than a normal cutting than a normal plant that you can quickly get them to the temperature and then back down again quickly whereas a a large corm or bulb or tuber you could think you can get in the center of that tuber to 50 degrees celsius means much longer and the outside temperature will have to be a lot warmer so so yeah that's probably going to be lower success rate there what else can we say this is sort of the term is thermotherapy by the way so what else can we say about it you can do it on whole plants large plants but you would probably need a grow room dedicated to it with a sort of a temperature of high 30s probably early 40s for two to six weeks that's a lot of heat if you're not in a tropical or arid area but you've got fruit trees large fruit trees ornamentals that are just infected then it might be worth it for targeting systemic viruses and preserving the whole plant structure rather than going back down to cuttings and starting it all over again. The heat stress will reduce the vigour and survival of the plants. You'll probably get some scorching on the leaves and things like that. So if it's an ornamental plant, you might reduce that. The success rates for whole plant thermotherapy are lower. So 30 to 70% virus elimination. And just because the temperatures are lower, so the virus isn't exposed to such a high temperature. And maybe this is why, you know, when you get a virus, like a cold or a flu, your body heats up because viruses don't like high temperatures. But, you know, tropical plants still get viruses. So I'd imagine this is harder to do on tropical plants and easier to do on temperate plants, because tropical plants are going to be exposed to these high temperatures anyway, and the viruses will be adapted to them. It will depend on the virus and its genetics, because even though they're not alive, they have genetics, they have genes, whether that's RNA or DNA. So the virus biology will have an effect and the host tolerance the ability to withstand those high temperatures will be key and the precise treatment i would probably do a water bath would probably be the easiest way to do it with cuttings now a water bath you can set to a set temperature and and dunk them in what's that thing they use in kitchens is it a bain marie when they when they're cooking steaks very precise temperatures you could potentially use one of those as well and or Or if you fail in that, a pot on a stove or something in an oven, some water in an oven that could get the plants to 50 degrees Celsius uniformly. So you don't want to put them in dry heat in an oven because they're exposed to all sorts of temperatures there. Definitely don't just put them in an oven. Definitely use a water bath for cuttings and things like that. So that would be my top tip. Just sort of Google there. You can pick up a Bain-Marie for like 100, 140 pounds. So that's not a lot considering the value if you're going to go to these lengths then the value of these plants must be considerable if you're going to spend the time and effort to try and eliminate viruses from them and potentially you know with virus testing getting better and better and more what's the word i'm looking for accessible you could potentially have a nice little hydroponic. Business selling certified virus-free heat treated cuttings that could be one of the things if you if in your industry cuttings there's a there's a business is selling cuttings and you're looking for a unique selling point then potentially you could say our product our cuttings are all heat treated and checked and checked for viruses before they leave the nursery and that could be a really good small little venture little bootstrapped hydroponic company to get you going up and running, selling, cuttings, and propagation material. Anyway, that's been Hydroponics Daily for today. If you found it interesting, please do give us an Apple podcast review because it does help spread the word of hydroponics with the wider horticultural gardening community and scientific community. If you're not an Apple, just make sure you follow the podcast so you don't miss an episode. We've got about 14 episodes left of 2025. I've done an episode every day, at the very least check out www.Eutrema.co.uk for all your amazing. Fertilizers, biostimulants and biopesticides. None of our products control viruses because you can't control a virus. You have to either destroy your plants or heat treat them. You can use insecticides to prevent the spread of aphids, which transfer the viruses. We don't sell insecticides, we sell an insecticide or soap and that's about it. So yeah, that's been Hydroponics Daily for today. Thank you very much for listening and I'll see you again tomorrow. https://eutrema.co.uk/shop/fertiliser/liquid-gold-unique-complete-fertiliser/ Roger Hull — John Innes Centre David Baulcombe — University of Cambridge James Carrington — Donald Danforth Plant Science Center Andrew O. Jackson — University of California, Berkeley B. W. Falk — University of California, Davis Anne Simon — University of Maryland Herman Scholthof — Texas A&M University Siddarame Gowda — University of Florida Ralf Georg Dietzgen — University of Queensland Ioannis E. Tzanetakis — University of Arkansas Bryce Falk — University of California, Davis Karl Maramorosch — Rutgers University John Hammond — USDA Agricultural Research Service Robert A. Owens — USDA Agricultural Research Service Véronique Brault — INRAE Thierry Candresse — INRAE Stephane Blanc — INRAE Yiguo Hong — Zhejiang University Shou-Wei Ding — University of California, Riverside W. Allen Miller — Iowa State University Karen-Beth G. Scholthof — Texas A&M University Scott Adkins — USDA Agricultural Research Service Hanu R. Pappu — Washington State University Michael J. Adams — Rothamsted Research John Walsh — University of Warwick Peter Palukaitis — Seoul National University Said Ghabrial — University of Kentucky Rajagopalbabu Srinivasan — Texas A&M University Feng Qu — Ohio State University Michael M. Goodin — University of Kentucky Yongliang Zhang — Chinese Academy of Agricultural Sciences Xueping Zhou — Zhejiang University Shahid Siddique — University of Tennessee Ping Qian — Fujian Agriculture and Forestry University Shouhua Feng — Chinese Academy of Sciences Satyanarayana Tatineni — USDA Agricultural Research Service Aiming Wang — Agriculture and Agri-Food Canada Feng Li — University of South Dakota Jinling Huang — East China Normal University Byungwook Ahn — Seoul National University Chikara Masuta — Hokkaido University Nobumichi Saitoh — University of Tokyo Tetsuo Meshi — Kyoto University Kei Fujiwara — University of Tokyo Masayuki Ishikawa — National Institute of Agrobiological Sciences (Japan) Toru Fujiwara — University of Tokyo Sung-Hwan Yun — Seoul National University Kook-Hyung Kim — Seoul National University Yijun Zhou — Nanjing Agricultural University Jianping Chen — Chinese Academy of Agricultural Sciences Fengming Song — Zhejiang University Shou-Wei Ding — University of California, Riverside Jean-Michel Hily — INRAE Christophe Ritzenthaler — CNRS Hugues Vigne — University of Strasbourg José-Antonio Daròs — IBMCP-CSIC Ricardo Flores — IBMCP-CSIC Vicente Pallás — IBMCP-CSIC Pedro Moreno — IVIA Valencia María Teresa Gutiérrez — University of Granada Eugene S. Dennis — CSIRO Peter Waterhouse — Australian National University Mikhail Pooggin — Friedrich Miescher Institute Thomas Hohn — University of Basel Michael J. Oliver — USDA Agricultural Research Service Gary P. Munkvold — Iowa State University William O. Dawson — University of Florida James Schoelz — University of Missouri Claudio L. Bassett — USDA Agricultural Research Service Jorge A. Sánchez-Navarro — IBMCP-CSIC Rongxiang Fang — Chinese Academy of Sciences Yijun Qi — Tsinghua University