Could fungi reduce our dependence on chemical fertilizers?

For more than 500 million years, a large fraction of land plants exist in a mutually beneficial, symbiotic relationship with arbuscular mycorrhizal fungi. The plants share their carbohydrates with the fungi that inhabit their roots. In exchange, these fungi provide plants with nitrogen and phosphorus, and improve the stress resistance of their host. This ancient mutualism has the prospect of making agriculture more sustainable by reducing the need for chemical fertilizers, says Professor Heike Bücking.

Dr Bücking, from South Dakota State University Department of Biology and Microbiology, has been studying such ecological relationships in food and bioenergy crops including wheat, corn, soybeans, alfalfa, clover and perennial grasses, such as prairie cordgrass. She is considered a pioneer in her field with numerous publications to validate her achievements.

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Doctoral student Arjun Kafle and professor Heike Bücking of the South Dakota State University Department of Biology and Microbiology examine soybeans to explore the complex interactions between plants and beneficial microorganisms that improve the nutrient uptake and stress resistance of crops (http://bit.ly/1qCOqfQ)

Her research has been supported by the National Science Foundation, South Dakota Wheat Commission, Sun Grant Initiative, Soybean Research and Promotion Council and the U.S. Department of Energy — Joint Genome Initiative.

In order to define the plant-fungi relationships, Bücking collaborates with researchers at the Vrije Universiteit in Amsterdam and the University of British Columbia as well as other South Dakota Agricultural Experiment Station researchers. “Though a host plant is colonized by multiple fungi species simultaneously, the plant knows exactly where certain benefits are coming from. The host plant can distinguish between good and bad fungal behavior and allocates resources accordingly,” she said, noting that the host plant transfers anywhere from 4 to 20 percent of its photosynthetically fixed carbon to mycorrhizal fungi.

These fungi are seen as living fossils and explore the soil with its hyphae in the search for nutrients. They form networks that give them access to multiple hosts. Her research showed that when host plants were shaded and thus decreased their carbohydrate allocation, fungi responded by reducing their nutrient share. “We think these fungi have the potential to increase the biomass production of bioenergy crops and the yield of food crops and do so in a more sustainable and environmentally friendly way,” said Bücking.

She and her collaborators, in an attempt to optimize fungi for specific crops found that some fungi are more beneficial than others. They arrived at this conclusion when they carried out exhaustive analyses on the relationship between alfalfa and 31 different isolates of 10 arbuscular mycorrhizal fungal species.

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The Garden’s Do-Gooders: Close up of a root hair infected with mycorrhizae (http://bit.ly/1SYFTgu)

However, those that benefit one crop may not provide the same nutrients or benefits to another crop species, she cautioned. “Even different isolates of one fungal species can behave differently, and it will be necessary to identify fungi that are optimally adapted to their specific environment and host plant to get the highest plant benefit.

In addition to their role in plant nutrition, these fungi play an important role in the plants’ adaptation to stressors. For instance, they can protect food and bioenergy crops from environmental stresses, such as drought, salinity and heavy metals, and diseases. Bücking explained, “All the stresses that a plant can potentially be exposed to are generally improved by mycorrhizal interactions.”

However, she added, more research is necessary to better understand how this ancient symbiosis between land plants and fungi can be used to its full potential.

The above article has been compiled using the information from the article here.

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