Food for thought on su Producing enough food is a national priority in populous countries like India. So much so that the government provides subsidies to offset the cost of chemical fertilizers. Farmers rely on the fertilizers to maximize crop production and keep food prices affordable. But UWM microbiologist Gyaneshwar Prasad, who is from India, worries. Early in his career, he studied bioremediation – natural ways of cleaning up pollution – and he could see the problems that came with such a reliance on chemical fertilizers. Making artificial fertilizers requires a disproportionately large amount of fossil fuel, and fertilizers become less effective once a certain saturation point is reached. Moreover, an estimated 20 percent of those chemicals end up in agricultural runoff that pollutes water supplies. “There’s got to be a way to feed the world in a more sustainable fashion,” says Prasad, an associate professor of biological sciences. Prasad’s research centers on finding such a
solution. To do so, he’s following a path that nature has already laid out, and it has tantalizing possibilities. For most plants, growth is limited by the amount of nitrogen available in soil, which is depleted over time. But legume crops – such as beans, peas, lentils and alfalfa – have a partnership with certain soil microbes. These microbes provide the plants with an unlimited supply of nitrogen in exchange for nutrients that the plant makes from photosynthesis. This process, known as nitrogen-fixing, creates a natural fertilizer for the plant, but it mainly happens with one kind of bacteria – rhizobia. Discovering how to transfer rhizobia’s nitrogen-fixing ability in legumes to other staple crops has become something of an agricultural holy grail. Half of the world’s food energy comes from varieties of three cereal crops: wheat, rice, and corn. “If we were able to reduce the amount of chemical fertilizer needed to grow cereal crops even just a little,” Prasad says, “the impact would be huge, especially in developing countries where individual farmers with small yields would benefit the most.” A long quest The idea of transferring rhizobia’s nitrogenfixing abilities to other crops is not new. Agronomists recognized the potential more than a century ago, and still, nobody has unlocked the mechanism behind it. When the soybean genome was sequenced about a decade ago, scientists expected they would find the fixation mechanism linked to a gene that other plants don’t possess. But that’s not what researchers discovered. In fact, the genes that legumes use for their symbiotic relationship with rhizobia also are found in the genomes of other crops.
Soybeans and other legumes interact with the bacteria rhizobia in a way that creates natural fertilizer for the plant.. (UWM Photo/Pete Amland)
6 • IN FOCUS • July, 2019
