From lentils to chickpeas and even plain baked beans, legumes are perhaps best known as an alternative, plant-based source of protein. These plants are environmental heroes: they work with soil microbes to “fix” nitrogen from the air, enriching the soil with nutrients to enable them to thrive.
As their nitrogen-fixing capacity becomes better understood, scientists hope to find ways to increase productivity and eventually apply some of these effective soil-enriching properties to other crops, such as grains. Thanks to its ability to fix nitrogen, crops will need less nitrogenous fertilizer and soil health will also improve.
Legumes, the edible dry seeds of legume plants, are a staple in the diets of both humans and animals worldwide. While it is generally consumed as canned beans, chickpeas and lentils in Europe and the USA, black-eyed peas are among the most important legumes in sub-Saharan Africa.
Legumes, which contain high amounts of protein, carbohydrates, dietary fiber, vitamins and minerals, play a fundamental role in a nutritious healthy diet. Its seeds and leaves are also used as animal feed. For small farmers in developing countries, nutritious legumes are a cost-effective alternative to animal protein and make up a large portion of typical diets.
In Western Kenya, Rwanda and Burundi, people consume an average of more than 30 kg of beans per year, while many African countries recommend legumes as a meat alternative in their dietary guidelines. Legumes can also be stored for long periods of time without affecting their nutritional content.
The magic inside root nodules
About 100 million years ago, legumes evolved the natural ability to host beneficial bacteria inside specialized structures called root nodules. Here, bacteria convert gaseous nitrogen in the air and soil into a form that the plant can access as nutrients.
Therefore, legumes need less nitrogen fertilizer than grain and other vegetable crops. A high-performance legume can fix up to 300 kg of nitrogen per hectare; otherwise this would cost farmers around $1 per kg of fertilizer to meet the plant’s nutritional needs.
In the Enabling Food Symbioses in Agriculture project, we are trying to understand exactly how legumes do this. We are investigating how these nitrogen-fixing root nodules first evolved only in legumes. With this knowledge, we hope to find ways to increase the efficiency of nitrogen fixation in root nodules and maximize the growth and yield of legume plants.
beneficial bacteria
My research group investigates how legumes can interact with beneficial bacteria and avoid disease-causing microbes. While bacteria such as rhizobia in these root nodules help plants provide a nutrient source, other soil microbes, including bacteria and fungi, can cause disease and prevent plants from converting more nitrogen. In other words, the plant must have a defense mechanism to keep disease-causing microbes away. This may also prevent it from fully interacting with beneficial bacteria.
Our research team identified potential factors that limit nitrogen fixation in nodules. MedicagoAlso known as barrel doctor or barrel clover. This legume is often used for research purposes and is not grown for consumption. By studying these limiting factors, we hope to improve the efficiency of nitrogen fixation without affecting the built-in defense mechanisms that protect the crop from diseases.
Researchers studying this mechanism in research legumes are studying several related legume crops, such as soybeans and cowpeas, to understand how widespread and applicable the underlying biological mechanisms are and whether they can be exploited to improve other legumes in the future.
Despite being one of the oldest domesticated crops, many legumes are much less adapted to agriculture and therefore have significant potential for further development through breeding and genetic engineering, making them more suitable and sustainable for modern food systems.
Benefits of more effective nitrogen fixation in legumes would include greater growth and biomass and higher protein content in the seeds or legumes. This will increase the nutritional value per crop and means more high-quality, nutrient-rich food can be produced per hectare.
Higher yields will create new opportunities for small-scale and subsistence farmers to grow and utilize legumes such as soybeans as cash crops to improve rural livelihoods. More productive legumes may be more effective as a rotation crop that improves soil health; This is especially important for farmers dealing with degraded soil, such as those found in sub-Saharan Africa.
The more we know about this unique ability of legumes, the better our chances of successfully developing other crops with similar abilities. Such a development, albeit several years away, could transform sustainable agriculture, especially in regions where access to synthetic fertilizer is already limited due to cost and availability.
Extending nitrogen fixation to other crops has long been the ambition of crop scientists worldwide, and the pace of progress is accelerating as plant biology studies advance.
This article is republished from The Conversation under a Creative Commons license. Read the original article.
Sebastian Schornack receives funding from Bill and Melinda Gates Agricultural Innovations. He is also listed as the inventor of a patent filed by the University of Cambridge on a gene that limits nitrogen fixation.