b'Crops that Fertilize ThemselvesA progress report on achieving nitrogen fixation in corn and other non-legume crops. By Treena Hein, Seed World ContributorNO MATTER A SEEDS GENETICS,nitrogen fertilizer isroots that secrete a rich mucilageand in that carbohydrate-critical for achieving high yields, especially in corn.rich medium are many species of bacteria with the ability to fix nitrogen. That is, they can capture nitrogen from the air and the Just try to grow corn without it, says associate professorcorn plant absorbs it, in some respects similar to how carbon Jason Wallace at the Institute of Plant Breeding, Genetics &is captured directly by the plant itself through the process of Genomics at the University of Georgia. But its costly for thephotosynthesis. farmer and has significant environmental impacts. Indeed, ferti- The results have been breathtaking. Field assessments over lizer costs are expected to stay high, and its estimated that onlyfive years indicated that in this corn, atmospheric nitrogen fixa-40-60% of synthetic fertilizer ever reaches the crop. Nitrogention contributed up to 82% of its nitrogen needs. Its interesting emissions from fertilizer applications are also a significant sourceto note that the corns performance had already been improved of global GHG emissions.to some extent through selective breeding by Sierra Mixe farmers. Wallace explains that if he can reduce the amount of nitrogenNow with funding from the U.S. Department of Agriculture, fertilizer needed by a crop by even 5%, even that small differ- An is examining how these bacteria fix nitrogen with his col-ence would have enormous impact. He adds that there areleagues, including Wallace and Professor Natalia de Leon at UW places in the world farmers cant afford nitrogen fertilizer. It iswho are crossing Mexican landraces with U.S. Midwest-adapted very exciting that our work could increase yields for these farm- varieties. Other collaborators include Brian Pfleger at UW ers and lift their families out of poverty. Madison and Wilfred Vermerris at the University of Florida.The work Wallace is referring to is a collaborative effort toBut corn is not the only crop to be found with the trait. breed corn that acquires its own nitrogen from the air. ThisSorghum was discovered in Africa that does the same thing, research is being led by Professor Jean-Michel An at UniversityAn says. We have already published a preliminary look at this of Wisconsin (UW), but it all began many years ago in thevariety and found that atmospheric nitrogen fixation meets nitrogen-depleted soils of Sierra Mixe, in Oaxaca, Mexico. about 43% of its needs, without any breeding improvement by local farmers. We are also in the process of publishing a paper Discovering Natural Nitrogen Fixation in Mexico that shows the genetic trait is similar in maize and sorghum. Its In 2009, An was approached by other colleagues to validatevery exciting that the number of nodes that carry aerial roots nitrogen fixation in an Indigenous landrace of maize grown inseems to be controlled by two or three genes in both.Sierra Mixe. This maize sported extensive networks of aerial 38/ SEEDWORLD.COMSEPTEMBER 2024'