Plants and microbes have always been closely connected. Symbiotic fungi are thought to have supported the early colonisation of land by plants around 470 million years ago by improving nutrient uptake. Direct fossil evidence of arbuscular mycorrhizal fungi is around 400 million years old. But they are not the only unseen helpers in the soil. Bacteria belong here too, such as rhizobia, which colonise the roots of legumes and trigger the formation of root nodules there, in which the bacteria convert atmospheric nitrogen into compounds the plant can use.

With the Green Revolution, high-yielding cereal varieties spread in particular from the 1960s onwards. In wheat, short-strawed, lodging-resistant varieties with resistance to rust fungi were a decisive breeding success. Together with improved nutrient supply, irrigation and further cultivation methods, they made considerable yield increases possible. The accompanying intensification of agriculture did, however, also bring ecological burdens with it, for example through excessive fertilisation and high water consumption.

Researchers today are examining how beneficial plant–microbe interactions can be promoted in a targeted way and harmful ones limited. Modern breeding methods, genomics and synthetic biology are intended to help match plants and microbial communities to one another so that crop plants use nutrients more efficiently and become more resistant to plant diseases. Under suitable conditions this could reduce the need for mineral fertilisers and chemical-synthetic pesticides. Despite scientific progress, many questions remain open: how do plants regulate the balance between defence and cooperation under changing soil and environmental conditions? Why can experimental results not always be transferred reliably to the field? Whether a partnership is established and benefits the plant depends on the species and genotypes involved, the microbial communities present and the soil and environmental conditions. Management also plays an important part: crop rotation, fertilisation and tillage influence microbial life in the soil.

Further research is therefore needed in order to decipher the complex interplay of plants, microbes and the environment and to use it responsibly. With a better understanding of these underground networks we can, in the long term, help to shape an agriculture that works more sustainably and more sparingly with resources.

Plants and microbes have been closely interlinked for a very long time. Symbiotic fungi are thought to have supported the early colonisation of land by plants around 470 million years ago by improving nutrient uptake. This assumption rests on molecular and fossil evidence and has not been conclusively proven; the oldest direct fossil evidence of arbuscular mycorrhizal fungi is around 400 million years old. Fungi are not the only soil organisms in this role. Bacteria belong here too, for instance the rhizobia, which colonise the roots of legumes and trigger the formation of root nodules there, in which they convert atmospheric nitrogen into compounds the plant can use.

With the Green Revolution, high-yielding cereal varieties spread in particular from the 1960s onwards. In wheat, short-strawed, lodging-resistant varieties with resistance to rust fungi were a decisive breeding success. Together with improved nutrient supply, irrigation and further cultivation methods, they made considerable yield increases possible. The accompanying intensification of agriculture also brought ecological burdens with it, for example through excessive fertilisation and high water consumption.

Research today examines how beneficial plant–microbe interactions can be promoted in a targeted way and harmful ones limited. Modern breeding methods, genomics and synthetic biology are intended to help match plants and microbial communities to one another so that crop plants use nutrients more efficiently and become less susceptible to plant diseases. Under suitable conditions this could reduce the need for mineral fertilisers and chemical-synthetic pesticides. No finished procedures have emerged from this so far.

Whether such an interaction is established and benefits the plant depends on the species and genotypes involved, on the microbial communities already present in the soil and on the soil and environmental conditions. Management also has an effect: crop rotation, fertilisation and tillage influence microbial life in the soil. Correspondingly many questions remain open. How do plants regulate the balance between defence and interaction under changing soil and environmental conditions? Why can experimental results not always be transferred reliably to the field? Further research is to decipher this interplay; in the long term the knowledge is intended to make agriculture more sustainable and more sparing of resources.