Climate change

New diseases poised to attack

Publié le 01/05/2023 - 10:53

Originally a disease affecting rice, virulent strains affecting wheat were first detected in South America and then Turkey. Ombee/AdobeStock.png

“The  prospect of the arrival of new diseases that are very devastating to crops has the advantage of mobilizing many researchers, says Thierry Langin, research director at the CNRS and head of the small-grain cereal disease team within the UMR Inrae GDEC in Clermont-Ferrand. Consequently, knowledge acquisition is faster.”

Wheat blast

“Mycosphaerella” mainly affects farms in Poitou-Charentes and Brittany. The shortening of the crop cycle in recent years tends to keep the expression of the disease at bay thus reducing the amount of harm it does. Terres Inovia
One example relates to wheat blast. While no cases appear to have been identified to date in France, research is already under way on this new disease to identify effective control strategies. It was originally a disease affecting rice and known to be particularly devastating. Virulent strains affecting wheat were first detected in South America. Since then, the disease has arrived to Europe’s doorstep with cases detected in Turkey. Hence the potential risk that the disease will appear in France one day, especially considering that at least two vectors are known. The first, the easiest to understand, is the unfortunate import into France of virulent strains through contaminated wheat. Given the importance of the international wheat trade, the probability of this happening is unfortunately not zero. Especially since climate change is bringing about conditions in France that could, today or tomorrow, favor the development of this disease.
The second is the mutation of virulent strains in other plant species, particularly turf, which could then attack wheat. The probability that one or the other of these scenarios will occur, demands effective control strategies today. “Researchers are already working on identifying gene pools that are resistant or partially resistant to this disease, says Thierry Langin. This ongoing work already enables us to propose sources to plant breeders to create suitable varieties. Implementation time depends on the genetic pool identified and its proximity to the crop species of interest. In any case, we are preparing for the possible arrival of wheat blast to France.”

Respond globally

The establishment of an effective epidemiological surveillance network is also helping to prepare for the arrival of new diseases. Its purpose: Very early detection of even the slightest source of future problems so that researchers can work upstream. Today, the goal is no longer to necessarily win a sprint against disease but rather to win a hurdles race, each hurdle representing an element of defense against disease. Even more so than before, genetic, agronomic and land management levers must be used simultaneously to build global responses.

An unexpected form of combat

When it comes to rapeseed, people are talking about Mycosphaerella which is becoming increasingly frequent and destructive. Today, this disease mainly affects farms in Poitou-Charentes and Brittany. Due to milder Autumns and Winters, it can start very early in the crop cycle. “However, we have observed that the shortening of the crop cycle in recent years tends to keep the expression of the disease at bay thus reducing the amount of harm it does,” notes Gwénola Riquet, disease control manager at Terres Inovia. We have observed a similar phenomenon in sclerotinia. The frequency of the onset of the disease has decreased significantly. We readily attribute this observation to shifts in the crop cycle. Rapeseed flowers approximately eight to ten days earlier than it did four years ago which means that weather conditions are less favorable for the development of the disease. It is often dry and especially still cool. The pressure of the disease therefore decreases, but the inoculum remains intact. The disease is far from having disappeared. One must therefore remain vigilant.

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