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A $1.7 million research grant has been awarded by the National Science Foundation to plant pathology professor Douglas Cook at the University of California, Davis, to fund research on nitrogen fixation in legumes, the plant family that includes peas, beans, peanuts and alfalfa.

Legumes are well known for their ability to "fix" or assimilate nitrogen from the atmosphere, with the help of certain bacteria that grow on the roots of these crop plants.

Researchers hope that the grant will eventually help lift the world's neediest farmers out of poverty, by leading to new crop plants that don't require applications of expensive nitrogen fertilizer.

The three-year award is one of 15 grants given to researchers around the country as part of the NSF’s Basic Research to Enable Agricultural Development, or BREAD, program. The five-year initiative, jointly funded with the Bill & Melinda Gates Foundation, supports international projects, providing funds to researchers in the United States and to their international collaborators.

“Our research is aimed at better understanding how, and to what extent, crop domestication has impacted plants’ ability to fix atmospheric nitrogen, which is critical for plant growth,” Cook said. “We’re looking for the genes that control nitrogen fixation capacity, in hopes that they will lead us to more efficient nitrogen-fixing legume crops.

Cook noted that the productivity of modern agriculture currently depends on the use of nitrogen fertilizers. These fertilizers are expensive to produce and mainly derived from fossil fuels, which are becoming increasingly difficult to extract from the earth. As a result, farmers in many resource-poor areas of the developing world, particularly in Africa, cannot afford to use manufactured nitrogen fertilizers, and the productivity of their crops suffers proportionally.

“Their inability to purchase nitrogen fertilizers further reduces their farm income in a downward spiral of low productivity and deepening poverty,” Cook said. “Finding ways to intervene in this cycle is vitally important for agricultural development.”

One alternative to using nitrogen fertilizers would be to develop crop plants that can produce their own nitrogen. Legumes are one family of plants that offers the potential for just such a solution.

“Legumes are able to make their own nitrogen fertilizer because they have ‘learned,’ in the evolutionary sense, to let nitrogen-fixing bacteria inhabit a set of highly specialized root cells, called a nodule,” Cook said.

The nodule is a living fertilizer factory — part plant and part bacteria — that produces readily available nitrogen on the root of a legume plant.

Consequently legumes have been important in agriculture for thousands of years. They reduce the requirement for costly, external fertilizer and increase soil fertility for nonlegume crops, such as wheat or corn, which are often grown in the same field during alternate years.

Centuries of crop domestication, which reduces genetic diversity in cultivated plant species, appear to have also lessened the ability of certain crop legumes to fix atmospheric nitrogen.

“Put simply, some crop legumes are less fit than their wild ancestors,” Cook said.

He and colleagues, including Rajeev K. Varshney of the International Crops Research Institute for Semi-Arid Tropics in India, will use the legume species known as the chickpea, or garbanzo bean, to explore how domestication has impacted nitrogen fixation in legumes. They intend to identify the genes that control nitrogen fixation and, in so doing, develop strategies for increasing the nitrogen-fixing capacity in many other legume crops.

The project will use recent advances in DNA technologies in combination with molecular-genetic analysis. The researchers will characterize the wild ancestors and the domesticated crop in the search for genes whose function has been made less efficient during the course of domestication. Once identified, those genes could potentially be used either in classical plant breeding or molecular approaches to improve the capacity for nitrogen fixation in legume crops.

A complete list of 2010 BREAD award recipients is available from the National Science Foundation at .

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