To ensure adequate protection against PepMV, mild isolates of both strains are required

August 2021

In practice, there are several different strains of the pepino mosaic virus (PepMV) that can cause problems for growers. The EPPO (European and Mediterranean Plant Protection Organization) Datasheet on PepMV says the following about this: “No resistance genes to PepMV are available in commercial tomato cultivars. Some accessions [...] are resistant to isolates of the EU strain. Whether this resistance holds against the other PepMV strains remains to be investigated.

One method currently applied in various countries to control the negative effects of PepMV infections is cross-protection. Protection against severe EU strain isolates requires an attenuated EU isolate, while an attenuated CH2 isolate is required to protect against aggressive CH2 isolates. In many instances isolates of the CH2 and EU strains occur in mixed infections, so for adequate protection mild isolates of both strains are required.”

Because the two aggressive strains (CH2/EU) often occur together in a mixed infection, the use of mild isolates that protect against aggressive isolates of both strains is recommended. This provides broader protection against damage by PepMV than when a single mild isolate is used. This is endorsed by EPPO, among others.

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The earlier plants are treated with mild strains, the more fully they are protected

August 2021

Cross-protection is a strategy with a preventive effect. Tomato plants must be treated with the mild isolates of PepMV before they can come into contact with aggressive isolates. The plant also needs a short period of time to build up full protection. It is therefore important to apply the mild isolates as early as possible.

The article “Multi-genotype cross-protection against Pepino mosaic virus in tomato” describes how young plants are inoculated with V10, a product made up of two mild isolates of the virus. Introducing a mild virus into a plant activates RNA silencing in the plant. RNA silencing is a process in which the plant protects itself against subsequent infections with similar viruses. A certain length of time is required before the plant can protect itself against pepino mosaic virus. After being treated with V10, there is a short period of time in which the plant needs to build up resistance. After this period, it can protect itself against aggressive isolates of the virus.

In summary, therefore, the earlier we inoculate a plant with a mild virus, the earlier the plant is protected. Moreover, young plants are also more susceptible to virus infection, so a mild virus spreads more rapidly through the whole plant at this stage.

Read the article for more information on the use of cross-protection against PepMV in tomato.

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Authorisation of crop protection products

August 2021

Wouldn’t it be great if innovative crop protection products could be authorised more quickly?

Several Dutch organisations are pleading with the government for shorter waiting times and faster processing times at the Dutch Board for the Authorisation of Plant Protection Products and Biocides (Ctgb). The agricultural and horticultural sectors would like to become more sustainable, but are held back by authorised green crop protection products being unavailable.

In the European Green Deal, the government and the sectors have agreed that green crop protection products and biological agents must become available more quickly for use in the Netherlands. Submitted authorisation dossiers remain on the shelf for far too long. “There are waiting times of three to four years.”’

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