As we walk around the produce at a grocery store, we tend to forget how fortunate we are to live in a global society and how unusual it is to have access to exotic fruits and vegetables that grow halfway around the world. Globalization has not only brought animals and plants out of their local niches, but now fruits and vegetables are grown in America that were only previously grown on the other side of the world.

Until the ‘80s, soybeans were only grown in Asian countries. Now, they are grown abundantly in the U.S., especially with the rise of vegetarianism, veganism and lactose intolerance in recent decades. Soybeans are a type of legume, and like most legumes, have a symbiotic relationship with Rhizobia, a genus of nitrogen-fixing bacteria. Rhizobia provide Nitrogen to the plant. However, because they were brought from Asia, the natural Rhizobia usually found with soybeans wasn’t found in American soil. To remedy this problem, commercial nitrogen fertilizer was used in soybean fields to ensure they could acquire enough nitrogen. With the use of commercial Rhizobia, soybean crop was sustainable in the US. However, soybean farmers continued to have problems with crop yields as their fields became infested with soybean aphids, a pest that causes up to 40% of soybean crop destruction.

Eventually, natural and commercially available Rhizobia became available to US soybean farmers. When researchers compared soybean crops grown with naturally-occurring (i.e. Rhizobia now present in the soil) versus commercial Rhizobia (that was used to inoculate the plants), they noticed fields using the naturally occurring Rhizobia had lower aphid infections than crops grown with commercial Rhizobia or the plants that were artificially fertilized with Nitrogen. They also found that commercial Rhizobia would compete and destroy the natural Rhizobia. This provides the first evidence that different strains of nitrogen-fixing bacteria can affect plant-pathogen interactions.

Although the mechanism by which Rhizobia protects the soybean from aphid infection is still unclear, this research from Penn State University has the potential for protecting other legume crops as well, increasing crop yields. It also opens doors for research into the mechanism by which plants protect themselves.

Discussion Question: What other benefits could come from using a naturally occurring bacterium versus the commercially cultured one in the farming industry?

Article: http://www.sciencedaily.com/releases/2009/04/090414110818.htm
Article from Penn State: http://live.psu.edu/story/3909