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Utrecht scientists discover that soil microbes have the potential to make plants immune against diseases, opening new possibilities for sustainable and pesticide-free food production. They publish their findings 25 September in Science Advances.

Around 30 percent of the world food production is lost to diseases before reaching consumers. Currently, diseases are controlled by applying huge amounts of toxic pesticides to the fields. Together with colleagues from China and the United Kingdom, Utrecht scientists have discovered that soil microbial communities naturally associated with young plants can protect plants against diseases during their whole life, opening new possibilities for sustainable and pesticide-free food production.

Utrecht Scientist Alexandre Jousset and George Kowalchuk investigated with their team the effect of the soil microbiome on plant-pathogens interactions. “Even when the pathogen is present, some plants remain unaffected. We wanted to find out why”, Jousset says. To examine this question they looked in tomato plants on a field that had been naturally infected by the bacterium Ralstonia solanacearum, a soil-borne plant pathogen that infects numerous economically important crops with the devastating wilt disease, or bruinrot in Dutch. Once infected, farmers have to destroy the entire harvest by law.

Our results shows that it is not necessary to eradicate the pathogen

Time travel

To discover the effect of soil microbiome for disease developments, they utilized a newly developed experimental system that allowed repeated sampling of individual plants in a non-destructive manner. This way the scientists had a times series of the micro-organisms that were present around the roots throughout tomato growths. “We could go back in time – long before the onset of the infection – and discover which micro-organisms were present around those plants that survived or succumbed to disease.” The microbiome of surviving plants were associated with certain rare and pathogen-suppressing bacteria like Pseudomonas and Bacillus.

It turns out the microbes in the soil make the plant resistant to the pathogen. This effect can be transferred to the next plant generation along with the soil. “Our results shows that it is not necessary to eradicate the pathogen”, says Jousset. “Instead, we can control the diseases by

promoting naturally-occurring beneficial micro-organisms around the roots of the plants. If you have the right community of micro-organisms at the start, you can add as many pathogens as you want and the plants won’t be ill.”

Sustainable agriculture

The findings can have huge implications for farmers, predicts Jousset. He expects farmers to be able to utilize specific microbial communities to increase plant tolerance against disease. “Crop losses to plant pathogens is an ever-increasing threat for agricultural production. We now have the tools to help farmers and growers and to develop a more sustainable agriculture.”

Zhong Wei, Yian Gu, Ville-Petri Friman, George A. Kowalchuk*, Yangchun Xu, Qirong Shen and Alexandre Jousset*
Science Advances, 25 september, DOI: 10.1126/sciadv.aaw0759
*authors are affiliated with Utrecht ľ�ϸ���Ӱ��