Plant–microbe communication: a discovery with real-world impact

In the 1970s, INRA researchers embarked on a daring challenge: the study of how plants interact with soil microorganisms. Their objective was to better understand the mechanisms at play, and subsequently pave the way for natural alternatives to nitrogen fertilisers—the extensive use of which was placing increasing pressure on the environment.

Plants cannot directly utilise nitrogen from the air. Instead, specialized microorganisms convert it into a form they can absorb. In legumes such as soybean or pea, these microorganisms are bacteria that live inside nodules, specialised plant organs formed on the roots. Over time, a close, unique and lasting symbiotic relationship develops between the plant and the bacteria. This form of symbiosis—known as mutualism— benefits both the plant and the bacteria.

Two decades later, the researchers identified additional key molecules involved in this dialogue. Produced by bacteria, Nod factors trigger the formation of nodules. More recently, similar molecules, known as Myc factors, were shown to be produced by soil fungi. Their role is to facilitate a different form of endosymbiosis—mycorrhization—which enables many plants, including cereals, to better absorb nutrients. 

These discoveries extend far beyond the scientific sphere. Thanks to industrial partnerships, these molecules are now used as agricultural biostimulants in several countries, leading to an average yield increase of about 3% and representing a tangible improvement in crop productivity.

The implications are manifold. Economically speaking, these innovations have already generated estimated gains of several billion euros worldwide, mainly in North and South America. Environmentally speaking, they pave the way for a reduction in nitrogen fertilisers, which are responsible for water pollution and greenhouse gas emissions.

Over the longer term, these advances could strengthen Europe’s agricultural self-sustainability, particularly by promoting the development of legumes to reduce nitrogen fertiliser use, enhance protein self-sufficiency, and increase cereal crop productivity.

These discoveries are pivotal, not only because they led to the identification of Nod and Myc factors, but also because they enable the long-term development of a comprehensive framework, spanning from the understanding of symbiotic mechanisms to the development, evaluation, and implementation of agricultural solutions.