ToBRFV and the role of rootstock

Confidence on every level – Rootstocks with endurance and vigor deliver high-performance


Tomato rootstocks are the basis of a highly productive crop. Healthy roots help enable good water and nutrition uptake, especially under harsh conditions. Strong rootstock with endurance and a good root system can support plant development, which may help minimize the severity of symptoms throughout the season.

We are conducting continued research on the role of rootstocks in ToBRFV transmission and resistance performance in substrate and soil. We are working to accelerate the penetration of high ToBRFV resistance in our rootstock portfolio while keeping the high level of agronomic performance our customers have come to expect from Vegetables by Bayer.

Root uptake of ToBRFV


In general, virus infection starts with a mechanical infection when workers are handling the head of the plant. The virus moves quickly to the head of the plant, which is the most active growing part, but also to the roots through the phloem.

In some cases, ToBRFV might infect the plant from drain water and/or substrate. To investigate this issue Bayer conducted an experiment at an independent institute to see how easily roots can be infected.

In the trial, young plants were grown until roots emerged from the underside of the normal rockwool planting block. These roots were then damaged and then a solution containing ToBRFV was applied to infect the roots. After six weeks the roots and the above-ground plants were tested for ToBRFV.

The results showed that the roots in the middle of the rockwool block (i.e., not the roots which were initially infected), showed very low levels of ToBRFV. The PCR values were around 32, indicating the presence of virus particles. In terms of biological relevance, it is insufficient to identify a genuine ToBRFV infection in the plant. In the leaves of the scion, no virus was detected at all, indicating that ToBRFV was not transported from the roots to the shoots of the scion. This result, which suggests little or no uptake of the virus from the roots, is in line with other research*.

*Ct stands for Cycling times. It is the number of multiplications of a specific part of the virus RNA that’s needed to detect the virus.

A Ct value less than 32 indicates the virus is present. A Ct value of more than 32 indicates the virus is no longer present.

Rootstock influence on scions and ToBRFV levels


There is little information about ToBRFV in the roots of tomato plants. The effect of the rootstock in relation to the scion and ToBRFV levels has not yet been investigated, so Vegetables by Bayer conducted trials under glasshouse conditions in The Netherlands.

The trial was set up as follows: A resistant and susceptible variety were each grafted onto a susceptible rootstock and a resistant rootstock. The scions were inoculated first with Pepino Mosaic Virus and a week later with ToBRFV.

Twelve days after inoculation, the ToBRFV concentration in the scion was measured. The susceptible scion showed a similar concentration of ToBRFV whether it was grafted to a susceptible or a resistant rootstock. The virus concentration in the scion was already high, and soon after, the first symptoms were visible. The resistant scions resisted the ToBRFV longer, and there was no influence from the rootstock, whether resistant or susceptible.

After 35-40 days, the susceptible scions showed severe leaf and fruit symptoms and the resistant scions showed some symptoms after 50 days. The experiment ended after 3.5 months, and the final examination showed hardly any leaf symptoms and no fruit symptoms in the resistant varieties, whether grafted on susceptible or resistant rootstocks.

The experiment was conducted in early spring in the Netherlands, so light conditions were low, representing a difficult period of the year for tomato cultivation. As such, more experiments and research are needed as we continue the experiments to complement our knowledge and in turn, better inform you.

These trial results do not contradict the value of strong rootstock as a base for good production. A good rootstock provides advantages during the entire crop cycle. And strong rootstock with endurance and a good root system can support stronger plant development, which may lead to less severe infections throughout the season. Many growers and plant raisers tell us they prefer a strong rootstock with endurance. A new and less strong rootstock is seen as a higher risk for good production. Even if the rootstock is not resistant to ToBRFV, the power and the strength of the rootstock are a secure base to help enable the best production.

Reference: * A Novel Platform for Root Protection Applies New Root-Coating Technologies to Mitigate Soil-Borne Tomato Brown Rugose Fruit Virus Disease Eyal Klein 1, Elisheva Smith 1,2, Chen Klap 2,3, Elena Bakelman 2, Arie Ophir 2, Aviad Sela 3,4, Elena Poverenov 4, Dmitry Rein 5, Yachin Cohen 5, Dan Eliahu 6, Shai Shahal 6, Guy Mechrez 4, Karthik Ananth Mani 4, Pulikanti Guruprasad Reddy 7, Abraham J. Domb 7, Nadav Pass 1 and Aviv Dombrovsky 2,* 35 =  Dombrovsky, A.; Mor, N.; Gantz, S.; Lachman, O.; Smith, E.

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