How horticulture responds to ToBRFV threat

All over the world, the horticultural industry is doing everything they can to keep ToBRFV out. A US-Mexican collaboration is to identify extra tests and educate Mexican growers, the UK has done their homework and informs the industry via a webinar and the Dutch share their insights on how they keep their propagation material clean. 

With the highly transmittable ToBRF virus popping up on horticultural sites all over the world, the global horticultural industry takes measures to make sure their crop remains protected. How do they do it and what can be learned from each other? 

For an introduction on ToBRFV - please click here.

Mexico and US
A Mexican-US collaboration is to battle the virus on both sites of the border. The virus has been found on various growing sites in Mexico - although its remittance remains unclear - and there's also information on US contamination. Now a collaboration is to battle the disease and to spread contamination.

Iowa State University Seed Science Center (ISU-SSC) is working with SENASICA, the department of Agriculture in Mexico, to help identify and stop the spread of ToBRFV. The Seed Lab at ISU is the largest public seed testing facility in the world, testing over 35,000 samples annually on 300 seed species, for 350 different pathogens.  

SENASICA sought help from Dr. Tracy Bruns, ISU-SSC seed pathologist, because she previously worked with the Mexican government to control a disease from the same family, on pepper seeds.  

“We are currently working to validate that our Tobamovirus testing methods pick up this new virus,” says Tracy Bruns, ISU-SSC seed pathologist.  “If we can figure out how to best test seeds, it will help insure that healthy seeds are being planted and hopefully limit the spread of this disease.” 

"But implementing effective testing is only part of the battle, educating Mexico’s farmers on the importance of rotating crops and other management tools is the other critical issue", she continues. That is why Bruns has partnered with a scientist from University of California–Davis who is working on management and grower education. Their work is funded by a grant from the American Seed Trade Association and the seed industry. 

Bruns says it comes down to simple economics. "Mexico’s growers don’t have the resources to do what we would do in the United States. Creative management tools need to be found,” Bruns says. “We are working together on many different fronts to stop the spread and impact of this virus.”
With ToBRFV not being detected in Canada by now, the Canadian industry is doing everything they can to keep it that way. "Biosecurity is your main defense as prevention is key", the Ontario government said earlier already. Even though yesterday's Tomato Brown Rugose Fruit Virus Information Session has been cancelled, the event should be rescheduled within some days. 

UK Webinar is worth a watch
Since ToBRFV is popping up all over the world, the British prepare themselves as well and they do so by sharing knowledge. As part of AHDB's response to this threat they are hosting a webinar with Adrian Fox (Senior Plant Virologist, Fera), Heiko Ziebell (Senior Scientist, Julius Kühn-Institut for Epidemiology and Pathogen Diagnostics), and Sharon Matthews-Berry (Plant Health Consultant, Defra) to update the industry with the latest information on this virus and recommendations for growers. 

The British are preparing themselves since they expect ToBRFV contaminated product to enter the UK at any moment. "We are currently in discussions with Defra to discuss what approach the UK authorities will take should ToBRFV be reported in the UK. Moreover, similar discussions are also taking place within wider EU forum through EPPO etc", the growers organisation TGA shares. They have set up a ‘one-stop shop’ for information on the virus and how best you can protect yourself against it.

Seed imports
Since the virus is transmittable via seed, various countries have upgraded their import requirements. Mexico has introduced phytosanitary measures for the testing of imported seed for sowing of host species and allege extensive positive test results on imported seeds originated from 14 countries from three continents, including Asia. Turkey implemented emergency measures in March already, requiring RT-PCR testing of imported tomato and capsicum seeds originating from Jordan, Germany, Israel, Italy and Mexico. 

Australia and New Zealand demand the seed be tested by a certified laboratory and implement emergency measures as well. "Global movement via seed appears to be the only credible explanation for the observed intercontinental movement of ToBRFV", the Australian government explains. 

For New Zealand, seeds have to be sourced from a pest free area, and places of production have to be tested by ELISA.

To keep the industry updated, the International Seed Federation regularly presents guidelines on how to test for the virus. This ISHI-Veg method is validated extensively on various performance criteria.

In professional horticulture, extensive seed checking is a standard procedure, a Dutch propagator explains. The Dutch industry has had their share of virus threats with for example ToCV last year and the bacterial threat Clavibacter before and they hope their experience will help them keeping out ToBRFV as well.

For example the companies only work with seed that is GSPP certified. The Good Seed and Plant Practices quality mark is a hygiene and quality assurance for starting material, a propagator shares. "Uninspected seed is a risk, so we do not want seed that is not inspected and we do not sow it either. We receive a request for this every year, but we do not do it. Not to experiment with, not to test. GSPP goes above anything." 

The protocols at Dutch propagators have been upgraded. "For example, nowadays we disinfect returned packaging material extra, twice instead of once. There are so many host plants and we don't want to take any risks. Hygiene is paramount." Similar measurements are taken everywhere. "We ask growers to disinfect the carts before we come to collect them. Afterwards we disinfect the carts ourselves once again upon arrival."  

Then there's clothing: the protocol says it has to be washed at ninety degrees to kill the virus. "It means you can replace your wardrobe every week - a pricey situation and the margins are small. But don't get me wrong: if this is what it takes, this is what will happen." 

While more information and scientific research is yet to be found, growers can also take extra steps themselves. "Consider measuring your measures," the propagators advise. "Make clear what you are doing, because just saying that you prioritise hygiene is not enough anymore." 

The advise is in line with what the UK ADHB organisation shares. Also here it's hygiene, hygiene and hygiene. "As the virus is primarily transmitted via contact, a suite of prophylactic measures termed ‘hygiene best practice’ should be followed to minimise the chances of the virus entering and spreading within a crop. These precautions should be applied routinely. This list is not exhaustive but gives measures recommended to minimise the risk of spread of contact transmitted pathogens including other viruses and viroids." 

In Netherlands it's not just the propagators doing everything in their power to deal with the situation. Also within the production greenhouses strict hygiene measures are taken. Doors are and remain locked and visitors aren't welcome anymore. In the current situation, insecurity about the possibility to get rid of the virus after detection plays a big role. Therefore in the Netherlands the news on the German outbreak last year is followed closely. The latest information is that after following a strict hygiene protocol, the virus so far hasn't returned in the new season. 

The virus threat causes Dutch growers to reconsider growing tomatoes, thinking of switching to cucumbers. Risk avoidance plays a role in this, combined with the high level of efficiency in Dutch greenhouses. The Dutch industry has optimized production in such a way that the margins on production are low and the least disruption already causes a fall in profitability. 

Also in the Dutch breeding industry seed purity is of highest importance. "All seeds are tested for this, and other, viruses. Also efforts are made to develop resistances, but not much is known about it", Franky van Looveren with De Ruiter Netherlands explains.

At Syngenta they also have to deal with growers closing the doors of their greenhouses. Trials can't always be visited and their own demo greenhouse remains shut for the time being. The sector's response and the measures that are currently being taken are similar to when the pepino mosaic virus emerged, says Kris Goen of Syngenta. "We learned a lot from that too. Now there is little scientific and practical information available about ToBRFV and based on rumors you cannot work. That makes the sector uncertain."

Syngenta has a group of researchers working on seed quality and seed health, and is also investigating whether and how resistance to ToBFRV can be built in. "Resistant varieties are the next step, but this will be a process of a few years anyway."

A number of measures have been taken to prevent the virus from spreading through seed. For example, employees have been instructed on measures to be taken when visiting growers. In addition to the standard strict hygiene measures that are taken during seed production and the standard seed treatment against Tobamo viruses, all batches produced are also tested for the presence of ToBRFV as an additional guarantee. 

Logically, the focus in the sector is currently on ToBRFV, but many in the industry believe that everyone should not be blinded. “In my opinion, much more is going to happen in the coming years. The sector is becoming more and more international and so, I fear, this will not be the last virus. That is only more reason to focus fully on hygiene and to get as much clarity as possible about which measures work.”

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