Posts Tagged: nitrogen fixation
Discovery could reduce nitrogen pollution, save farmers billions
Researchers at the University of California, Davis, have found a way to reduce the amount of nitrogen fertilizers needed to grow cereal crops. The discovery could save farmers in the United States billions of dollars annually in fertilizer costs while also benefiting the environment.
The research comes out of the lab of Eduardo Blumwald, a distinguished professor of plant sciences, who has found a new pathway for cereals to capture the nitrogen they need to grow.
The discovery could also help the environment by reducing nitrogen pollution, which can lead to contaminated water resources, increased greenhouse gas emissions and human health issues. The study was published in the journal Plant Biotechnology.
Nitrogen is key to plant growth, and agricultural operations depend on chemical fertilizers to increase productivity. But much of what is applied is lost, leaching into soils and groundwater. Blumwald's research could create a sustainable alternative.
“Nitrogen fertilizers are very, very expensive,” Blumwald said. “Anything you can do to eliminate that cost is important. The problem is money on one side, but there are also the harmful effects of nitrogen on the environment.”
A new pathway to natural fertilizer
Blumwald's research centers on increasing the conversion of nitrogen gas in the air into ammonium by soil bacteria — a process known as nitrogen fixation.
Legumes such as peanuts and soybeans have root nodules that can use nitrogen-fixing bacteria to provide ammonium to the plants. Cereal plants like rice and wheat don't have that capability and must rely on taking in inorganic nitrogen, such as ammonia and nitrate, from fertilizers in the soil.
“If a plant can produce chemicals that make soil bacteria fix atmospheric nitrogen gas, we could modify the plants to produce more of these chemicals,” Blumwald said. “These chemicals will induce soil bacterial nitrogen fixation and the plants will use the ammonium formed, reducing the amount of fertilizer used.”
Blumwald's team used chemical screening and genomics to identify compounds in rice plants that enhanced the nitrogen-fixing activity of the bacteria.
Then they identified the pathways generating the chemicals and used gene editing technology to increase the production of compounds that stimulated the formation of biofilms. Those biofilms contain bacteria that enhanced nitrogen conversion. As a result, nitrogen-fixing activity of the bacteria increased, as did the amount of ammonium in the soil for the plants.
“Plants are incredible chemical factories,” he said. “What this could do is provide a sustainable alternative agricultural practice that reduces the use of excessive nitrogen fertilizers.”
The pathway could also be used by other plants. A patent application on the technique has been filed by the University of California and is pending.
Dawei Yan, Hiromi Tajima, Howard-Yana Shapiro, Reedmond Fong and Javier Ottaviani from UC Davis contributed to the research paper, as did Lauren Cline from Bayer Crop Science. Ottaviani is also a research associate at Mars Edge.
The research was funded by the Will W. Lester Endowment. Bayer Crop Science is supporting further research on the topic.
Editor's note: Blumwald is affiliated with UC Agriculture and Natural Resources through the Agricultural Experiment Station at UC Davis./h3>/h3>
As you're ladling up country-style pinto beans for your weekend barbecue or fixing a cold three-bean salad from kidney, string and navy beans for a summer picnic, pause to remember what a long and storied history these “common bean” varieties share and the new scientific advances that promise to boost their productivity worldwide.
This week, a new genome sequencing is being reported for the common bean, which ranks as the world's 10th most widely grown food crop and includes the culinary favorites above, whose varieties together comprise a $1.2 billion crop in the United States.
“The availability of this new whole-genome sequence for beans is already paying off,” said Paul Gepts, professor in the Department of Plant Sciences at UC Davis and co-author of the new sequencing study.
Gepts, who leads the bean-breeding program at UC Davis, notes that the new sequence is being used to confirm many of the findings made earlier by his UC Davis research group, including identification of the common bean's two points of origin and domestication.
Sequencing and bean ancestry
The common bean is thought to have originated in Mexico more than 100,000 years ago, but -- as the Gepts group earlier discovered – was domesticated separately at two different geographic locations in Mesoamerica and the southern Andes.
“This finding makes the common bean an unusually interesting experimental system because the domestication process has been replicated in this crop,” Gepts said.
The sequencing team compared gene sequences from pooled populations of plants representing these two regions and found that only a small fraction of the genes are shared between common bean species from the two locations. This supports the earlier finding that the common bean was domesticated in two separate events -- one at each location -- but distinct genes were involved in each event.
The new whole-genome sequencing is also helping to identify genetic “markers” that can be used to speed up breeding of new and more productive bean varieties in the United States, East Africa and elsewhere, Gepts said.
The nitrogen connection
All of bean varieties that belong to the “common bean” group share with the closely related soybean the highly valued ability to form symbiotic relationships with “nitrogen-fixing” bacteria in the soil.
The plants and the bacteria work together to convert nitrogen in the atmosphere into ammonia – which includes nitrogen in a form that enriches the soil and feeds crops. Nitrogen-fixing crop plants can actually reduce or eliminate the need for farmers to apply expensive fertilizers.
One goal of the new sequencing project was to better understand the genetic basis for how such symbiotic relationships between nitrogen-fixing plants and bacteria are formed and sustained, with an eye toward increasing fuel- and food-crop productivity.
The research team successfully identified a handful of genes involved with moving nitrogen around, which could be helpful to farmers who intercrop beans with other crops that don't fix nitrogen.
Findings from this study are reported this week online in the journal Nature Genetics. The sequencing project was led by researchers at the University of Georgia, U.S. Department of Energy Joint Genome Institute, Hudson Alpha Institute for Biotechnology and North Dakota State University.