Crops Could Thrive With Less Fertilizer if They Make More Microbial Friends

By Erik Stokstad

Plants growing in poor soil get by with a little help from their friends, gaining additional nutrients with help from neighboring bacteria and fungi. A newly identified mutation could make wheat even more popular with the microbes, researchers announced today in Nature. By recruiting more fungal partners to unlock soil nutrients, the advance could one day allow farmers to apply less synthetic fertilizer to their wheat and potentially to other crops similarly modified.

The results are “really novel and spectacular,” says Heike Sederoff, a plant molecular biologist at North Carolina State University who was not involved with the study. Cheng-Wu Liu, a plant molecular biologist at the University of Science and Technology of China, who was also not involved, adds that the discovery shows potential for developing more sustainable agriculture.

Industrial fertilizer, rich in synthetic nitrogen, phosphate, and other chemicals that fuel plants, is a double-edged sword of modern food production. Applying it to fields will nourish crops, especially wheat and other cereals that yield high-protein grain. Yet excess nutrients can cause environmental problems, polluting groundwater, for example, and the release of climate-warming gases.

Some of this leftover nutrition remains locked in the soil, accessible only to certain microbes. Plants won’t bother to ask for their help if farmers keep applying more fertilizer. But what if scientists could coax crops to tap these nutrients by expanding their circle of microbial friends?

To do that, researchers have been trying to understand how roots recruit beneficial microbes. Plants called legumes—which include peas and beans—grow nodules that house bacteria. In exchange for food from the plant, these bacteria provide biologically useful nitrogen. Legumes and most other crops also have a mutually beneficial relationship with certain kinds of fungi. The crops’ roots provide carbohydrates to their fungal friends, while they give the plant phosphate, and pass along some nitrogen and water from their extensive network of filaments in the soil.

Setting up all of these plant-microbe relationships takes a little molecular courtship. Plants in need of more nutrients or water exude compounds called flavonoids into the soil that attract beneficial microbes to their roots. One important part of this ritual takes place inside the nucleus of a plant’s root cells, where the concentration of calcium ions rises and falls at a particular frequency.