Plants recruit soil bacteria to protect against downy mildew, forming a leaf-based defense system. The bacteria not only combat pathogens but also leave a protective legacy in the soil for the next plant generation. This discovery, published today by Utrecht University biologists, offers a promising path toward creating crops that naturally fend off diseases, reducing reliance on harmful pesticides in agriculture.
At the Institute of Environmental Biology at Utrecht University (UU), microbiologists study how plants and soil microbes reciprocally influence and protect each other. "Soil bacteria are important for plant health," says researcher Roeland Berendsen. "Following infection of the laboratory model plant Arabidopsis thaliana by downy mildew, plants promote the growth of a very specific set of plant-protective bacteria." It appears that plants, figuratively, cry out for help, and specific microbes come to the rescue.
The Utrecht scientists, including the shared-first authors Pim Goossens and Jelle Spooren, found that especially the composition of bacteria on the plant's leaves changes after infection with downy mildew, a fungus-like micro-organism. Goossens: "On the above-ground parts of the plant, we found that a very small number of bacterial species was highly abundant on infected plants and that these bacteria limit the growth of the pathogen on the plant."
The researchers then compared the bacterial community on infected plants in Utrecht with those in laboratories abroad. "Hundreds of thousands of different species of bacteria exist worldwide", Goossens says. "But to our great surprise, we found exactly the same dominant bacteria on infected plants from labs in Germany and England."
Plants appear to attract these bacteria from the soil, after which the bacteria accumulate on the leaves, where they can protect the plant. Berendsen: "After the plant dies, those bacteria again survive in the soil. A new generation of plants directly benefits from that protective legacy as the good bacteria immediately colonize the young plant."
Crops create their own disease-resistant soil
The scientists are hopeful that their new results will be useful in agriculture in the future. Current agricultural practices rely heavily on the use of chemical crop protection that can be damaging for the environment." says Berendsen. "Now we know that plants can assemble a beneficial microbiome, we can make use of that in agriculture."
This knowledge could help make crops less dependent on pesticides. Berendsen: "For Arabidopsis plants, we now know which specific bacteria the plant recruits when infected with downy mildew, and we have an excellent basis to find out which mechanisms and genes are involved in this disease-induced recruitment by this model plant. We can then translate these fundamental findings to more economically relevant crop species. We think crops can ultimately be bred in such a way that they consistently create their own disease-suppressive soil."
This study was the result of a collaboration between the research groups Plant-Microbe Interactions (led by Prof. Corné Pieterse) and Translational Plant Biology (led by Prof. Guido van den Ackerveken).
Obligate biotroph downy mildew consistently induces near-identical protective microbiomes in Arabidopsis thaliana
P. Goossens, J. Spooren, K.C.M. Baremans, A. Andel , D. Lapin, N. Echobardo, C.M.J. Pieterse, G. van den Ackerveken, R.L. Berendsen
Nature Microbiology, 16 November 2023