Have you ever found brown spots hidden inside a leaf? Black spots in a potato? These are diseases caused by fungi or viruses: like any living thing, plants get sick. Their diseases affect the quality of harvested products and yield. For farmers, gardeners or gardeners, one of the solutions to prevent these diseases is to choose naturally resistant varieties.
An effective way: resistant varieties
Making varieties disease-resistant, both private breeders and public research have always been there. Thus, “in potato, we have important collections of plants with more than 30 related species that we test to detect sources of genetic resistance to diseases. Explains Jean-Eric Chauvin, research engineer * at INRA. This patient work is successful: 729 source plants resistant to the main agents of diseases of the potato – mildew, nematodes, viruses, … – have been made available to breeders by INRA since 1995! They are widely used to create improved varieties that meet the needs of consumers. Thus the genetic resistance to late blight, a fungus capable of annihilating a crop in about ten days, can now reduce by more than half the amount of fungicides used.
* Director of the Experimental Unit ” Plant Genetic Resources in Ocean Conditions” – INRA: National Institute of Agronomic Research
In cover, a photo of the resistance to late blight of potatoes in the field (in the absence of any chemical treatment): the brown foliage corresponds to the sick susceptible plants, while the green foliage corresponds to the resistant plants that remain healthy .
In vegetable plants, enormous progress has been made from this point of view, such as the resistance to Fusarium wilt of melon, very harmful in humid conditions, or the mildew of tomato destined for the cannery. Often varieties accumulate resistance to several aggressors. The use of resistant varieties not only reduces phytosanitary treatments, but also secures supplies. “Our market gardeners and retailers expect a stable quality of vegetables , and it is achieved mainly by disease resistance,” said Frédéric Cunot, Director France Bayer vegetable seeds.
In a large number of speciesthe criterion of disease resistance is also crucial. In the 2000s, breeders found among wild beets genetic resistance to rhizomania, a disease that wiped out sugar beet crops. This gene has been introduced by crossing into varieties, thus saving production, factories and several thousand jobs.
Avoid the development of diseases
The interest in plant resistance has taken on a predominant importance over the past ten years with the national plans for the reduction of phytosanitary products. Natural resistance is one of the simplest and cheapest ways to reduce the use of these products. So much so that the public means used for the creation of new varieties of potatoes are no longer dedicated to this aspect, and that in potagères it became the first selection criterion, before the yield.
But beware: “It would be unreasonable to think that genetic resistance will be able to do without phytosanitary products,” says Frédéric Cunot. This is why it is essential to combine all the existing means of struggle, such as turning different crops year after year on the same plot.
Tomorrow is getting ready
The breeders seeking to combine natural sources of resistance gene to make them as sustainable as possible. Advances in this area allow it. “Today we have enough sources of genetic resistance to potato late blight to consider gradually replacing all the old susceptible varieties ” concludes Jean-Eric Chauvin.