Bayer started researching sources of resistance when the virus first appeared in 2014
Susana García, Discovery Pathology Lead for EMEA, explains it all to Fruit Today Euromagazine.
What lines are you working on to find solutions for ToBRFV?
We have been working on it since the virus first appeared in Israel and Jordan and we saw that it could be a very serious problem due to the nature of the mechanical transmission, which is very efficient, and we understood that it could spread very fast to other tomato markets. We started to study the virus in that region in 2015, with the intention of giving solutions to the farmers with resistant varieties. When the virus was detected in Mexico, our efforts were expanded to other types of tomatoes in order to be able to give solutions to all the markets.
How long could it take to find a definite solution?
I think we are at a good place; the research is going in the right direction, but quality standards must be maintained. We have worked hard to find sources of resistance, locating the areas of the genome that provide this resistance through molecular markers and introducing them effectively in commercial tomato varieties. Normally, the resistance sources tend to have many negative characteristics associated to them that influence the flavour, the fruit size, yield, etc.; therefore, obtaining a commercial tomato with all the desired characteristics, including resistance, takes time.
Are some types more susceptible than others to suffer from the virus? Can it appear on other products?
To date, there are no commercial tomato varieties that are resistant to this virus, which is why, at present, everything on the market is susceptible to ToBRFV, although there are different levels of susceptibility. Additionally, when a plant is infected with ToBRFV, the seriousness of the symptoms can differ depending on the environmental conditions, the age of the plant at the moment of the infection, infections with other viruses and other abiotic stresses. The symptoms are similar to those produced by the well-known TMV. On the leaves: mosaics, chlorosis, flocking and leaf distortion, and faded yellow or necrotic spots on the fruit. Infections that are mixed with other viruses, such as Tomato spotted wilt or Cucumber Mosaic virus can cause more serious symptoms. Peppers are the hosts of the virus, but the resistance genes that most of the commercial hybrids have incorporated (L3 and L4) provide resistance against shrivelling. In principle, we are not having problems because this resistance has not been broken.
Are the steps taken by the sector sufficient to stop it from spreading?
The competent authorities are carrying out a magnificent job. For our part, we guarantee quality, pathogen-free seeds, since we work using the GSPP production system (Good Seed and Plant Practices), which is a hygiene and prevention system that concentrates on Clavibacter michiganensis spp (Cmm) in tomatoes and rootstock for protected crops, strictly following the latest plant protection standards and protocols with independent audits. In Almeria, we have an advantage because the first case has just been detected and we have a great deal of knowledge and information about how to handle and eradicate this virus, as opposed to when it was detected in Mexico, for example, when we didn’t know enough about it. We are open to whatever the sector needs, we have shared the experiences of farmers from Israel, Mexico and Jordan and we have given virtual talks in Mexico that have been very well received. We are capable of eradicating it, but emphasis must continue to be placed on prevention. If we are all responsible, marketing will continue without any problems. If we let our guard down, the outbreak expansion could be a problem.
What other problems continue to affect tomatoes? Are there any other important threats?
This year, Tomato Leafminer has been limiting for the sector. It has a greater effect in the spring, it appears in cycles. We continue researching other viruses that might not be as damaging as the ToCV or TYLCV. Although today we have resistances to TYLCV, we cannot relax our vigilance, as in countries such as Morocco or Italy recombinants of the TYLCV family have been found that could give more problems than others that we had here; and in Israel associations of TYLCV have been detected with other viral particles (satellites) that could breach resistance to TYLCV.