There is no curative control method making it possible to effectively control the viruses during cultivation, and in particular the tomato ( mosaic virus Tomato mosaic virus , ToMV). Usually, an infected plant will remain infected for the rest of its life.

We advise you to consult the “Protection methods” section of the sheet dealing with PepMV . In fact, the measures to control viruses transmitted by contact are the same, regardless of the virus. We will only report information specific to ToMV here.

Particular attention should be paid to the quality of the seeds , because they transmit this virus at a sometimes very high rate. If you have any doubts, they should be disinfected. For example, ToMV can be inactivated in seeds by dry heat treatment (thermotherapy: 80 ° C for 24 hours, 78 ° C for 48 hours or 70 ° C for 72 hours) or by trisodium phosphate. (Na ₃ PO ₄ ) at 10% for 30 minutes to 1 hour. We should also mention the method used at INRA in Avignon, which consists of treating the seeds in a 2% (v / v) solution of hydrochloric acid (HCl), and 3 g / l of pectinase. This enzyme ensures good separation of seeds and pulp. Subsequently, the seeds, once dried, are placed in an oven at 80 ° C. for 24 hours (dry heat). The combination of these two methods leads to the denaturation of the virus. Several other methods exist: discuss them with the engineers specializing in plant protection who will tell you which one is commonly practiced in your country.

As we have argued previously, several resistance genes are used to control ToMV:
- the “ gene Tm ” or “ Tm-1 ” , derived from Lycopersicon hirsutum , confers constitutive resistance. This gene appeared to be relatively unstable because it was quickly overcome by strains of ToMV of pathotype 1;
- the “ gene Tm-2 ” , located on chromosome 9, was obtained successively from various Lycopersicon peruvianum . This gene was found to be more stable than the previous one, although strains of pathotype 2 appeared as a result of its use, but at a slower rate. Let us point out a version “ Tm-2-nv ” which is associated with a semi-lethal “ gene nv ” inducing in homozygous tomatoes a network necrosis ( netted virescence );
the “ Tm-2 ² ” gene, an allele of the “ gene Tm-2 ” and of the same origin, is associated with defects in fertility and quality of the fruits in the homozygous state.

Like many hypersensitivity genes, " Tm-2 " and " Tm-2 ² " may no longer be effective at elevated temperatures. In addition, in the presence of a large inoculum linked to the proximity of a culture sensitive to ToMV, significant necrotic lesions can be observed on plants heterozygous for the " genes Tm-2 " or " Tm-2 ² " , this by generalization of the hypersensitivity reaction. This phenomenon occurs in particular in greenhouses where temperatures vary between 18-20 ° C at night and 35 ° C during the day.

In addition, as we have indicated previously, several strains or pathotypes have been shown to be able to overcome the “ genes Tm-1 ”, “ Tm-2 ” or “ Tm-2 ² ” , used alone or in combination. At least six pathotypes could be defined; their respective virulences are detailed in Table 49 bis .


Note that a strain called "M97" would bypass the resistance of the " genes Tm-2 " and " Tm-2 ² " of tomatoes. It could constitute an additional pathotype.

In order to make resistance to ToMV more durable, the selection strategy developed consisted in associating in the same genotype different genes at the origin of different mechanisms. For example, F1 hybrids, now cultivated in greenhouses, contain the following combinations of genes: “ Tm-1 ” “ Tm-2 ² ” / “ Tm1 ⁺ ” “ Tm-2 ⁺ ” or “ Tm- 1 "" Tm-2 "/" Tm-1 ⁺ "" Tm-22 "/ but above all" Tm-2 ² "" Tm-2 ⁺ ".

The premunity consisting artificially infect susceptible tomato plants with a "low" ToMV strain was used in the past to control the virus. Thus, the plants were protected from possible infections by aggressive strains, with much more marked symptoms. The weak strains used were obtained by random mutagenesis with nitrous acid. The hypoagressive strain MII-16 has been used to protect susceptible tomato cultivars under shelter in many countries in Europe, America, China, Japan and New Zealand. In France, although premunition was widely used, its use began to decline gradually at the end of the 1980s with the marketing of more and more resistant varieties. Remember that premunition has some limitations: it is not effective against TMV, and aggravated symptoms can be observed during infection with other viruses, such as CMV for example.

It should be noted that the “ gene N ” for resistance to TMV could be isolated from tobacco and transferred to sensitive transgenic tomatoes, thus conferring on them resistance to ToMV and TMV.


* Chemical control : As the number of pesticides available for a given use is constantly changing, we advise you to always confirm your choice by consulting the e-phy site of the Ministry of Agriculture and Fisheries which is an online catalog of plant protection products and their uses, fertilizers and growing media approved in France. This also applies to all biological products based on microorganisms or natural substances.