Discovery Could Decrease Reliance on Nitrogen Fertiliziers

A new discovery could represent the first step in decreasing the amount of nitrogen used by crops and, ultimately, the use of nitrogen fertilizer, which is known to disrupt the water systems where it is found.

Gary Stacey, a professor of plant sciences at the University of Missouri, discovered that many crops become "confused" when faced with the invasive but beneficial rhizobia bacteria. When the bacteria interact correctly with the plant, a symbiotic relationship is created in which the bacteria receive food from the plant and then produce the nitrogen needed by the majority of plants.

When legumes sense the bacteria they create nodules for it to gather and create the atmospheric nitrogen the plants need to stimulate their growth. However, this is not the case for all plants.

"There's this back and forth battle between a plant and a pathogen," said Yan Liang, a co-author of the study and post-doctoral fellow at MU. "Rhizobia eventually developed a chemical to inhibit the defense response in legumes and make those plants recognize it as a friend. Meanwhile, corn, tomatoes and other crops are still trying to defend themselves against this bacteria."

Stacey and Liang teamed up to treat a variety of plants with the bacteria and then monitor their reactions. As it turned out, all the plants received the signals and inhibited their immune system but the majority failed to carry out the final step of creating a home for the bacteria to thrive.

"The important finding was that these other plants didn't just ignore the rhizobia bacteria," Stacey said. "They recognized it, but just activated a different mechanism. Our next step is to determine how we can make the plants understand that this is a beneficial relationship and get them to activate a different mechanism that will produce the nodules that attract the bacteria instead of trying to fight them."