Plum pox is Bruno Darnaud's obsession.
This Drôme arborist knows it: if this virus, which has spread in European countries under the name of plum pox, attacks his peach and apricot trees, he would only have his eyes to cry.
“It is very complicated to fight against this type of virus, because there is no vaccine and the only solution is then to eradicate the contaminated trees.
But the National Institute for Agronomic Research (INRAE) may have found a revolutionary technology that would allow the fruit grower to rest easy.
INRAE researchers have indeed succeeded in modifying the DNA of a cherry tomato in a targeted manner in order to make it resistant to potyviruses, the largest group of RNA viruses affecting plants.
In his laboratory in Avignon, Jean-Luc Gallois works on the genetics and improvement of fruits and vegetables.
He observed that, among certain cultivated species, including peppers and peas, varieties (or plants) are naturally resistant to viral diseases.
Copy, Cut, Paste
“Some viruses use a plant protein to infect it, describes the virologist.
This protein actually has two functions: it is used by the virus and also serves the function of the plant.
However, the plants which resist the infection have acquired mutations in the gene which encodes this protein”.
These mutations, present for example in peas or peppers, make it impossible for the virus to use this protein while allowing the plant to live its life normally.
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Based on this observation, Inrae wondered if it could not transpose this mechanism to plants of agronomic interest.
Hence this test conducted on a cherry tomato.
Rather than attempt to inactivate the gene that makes the plant susceptible to the virus, the researchers modified it to mimic the mutations responsible for resistance.
How did they achieve this feat?
Using molecular scissors.
This technique with an unpronounceable name, baptized CRISPR-Cas9, makes it possible to modify a region of the DNA of the plant in a targeted and precise manner.
French researcher Emmanuelle Charpentier won the Nobel Prize in Chemistry in 2020 for inventing this process, which she believes could revolutionize the transition of the agricultural sector.
Aware of potyviruses… and pesticides?
“By modifying the DNA of the plant in a targeted manner, we modify the protein of said plant which the virus needs to develop,” explains Jean-Luc Gallois.
These changes give it strong resistance to several viruses of the potyvirus genus, including PVY.
PVY, also known as potato virus, is one of the most common viruses of plants of economic importance.
It is transmitted by at least 70 species of aphids and infects many plants, particularly belonging to the Solanaceae family
(tomato, pepper, pepper, etc.)
.
Once a plantation is affected, PVY can lead to yield reductions of up to 50%, and even 80% for susceptible varieties or in the case of co-infection with other viruses.
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By managing to make their cherry tomatoes resistant to these aggressive viruses, the INRAe researchers believe they have put their finger on "a proof of concept": in this case "the possibility of reproducing natural resistance in sensitive species and thus to limit the use of pesticides.
"As is the case with natural mutations selected in other species, these changes do not modify the expression or the accumulation of the protein produced by the gene, nor do they affect its function", specifies INRAE. .
Next guinea pig: the potato
In other words, summarize the agronomy researchers, “the plant with these mutations resists infection and for it, it does not change anything!
"By dint of testing mixtures of pollens, making selections and crosses, we have discovered certain varieties of apricot trees that are less susceptible to the Sharka virus, but it's a very long and very complicated job," admits arborist Bruno Darnaud.
All the research that goes in this direction can therefore help us.
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At the end of this experiment, INRAe thinks for its part that it can duplicate the “cherry tomato” operation for other species of fruit and vegetables.
"Currently, we are trying to transfer this resistance mechanism to potatoes," explains Jean-Luc Gallois.
We also have projects in collaboration with African countries on cassava and we could develop resistance to viruses for other plants such as beets or vines.
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