Legumes like soybeans, alfalfa, peas, beans, peanuts and many more have a remarkable ability: They can partner with soil bacteria called rhizobia to capture nitrogen from the air in a biological process called nitrogen fixation. It is a mutualistic relationship - both the plant and bacteria benefit - that provides nitrogen in an accessible form that is essential for plant growth and sustainable agriculture.
Not just any rhizobia will do, however, as specific rhizobia match with specific plants for the best crop outcome, according to a team led by Penn State researchers, who wanted to learn how specific plant genes determine which rhizobia can form relationships. In a study published in The ISME Journal, they describe the complex relationship between plant host genes and rhizobial genes, and how plant genes strongly influence which rhizobial strains plants chose from a diverse mixture.
"We identified a core set of rhizobial genes that altered bacterial strain success when plant genes were disrupted," said study senior author and team leader Liana Burghardt, assistant professor in Penn State's College of Agricultural Sciences. "Our results reveal how genetic mutations in plant hosts alter which genes are important for bacterial strain success, setting the stage for scientists to develop improved rhizobial strains for agricultural inoculants and breed legume hosts better adapted to field environments where many strains coexist."
Rhizobia live inside specialized structures on plant roots called nodules, where they convert atmospheric nitrogen into a form the plant can use, explained study first author Sohini Guha, postdoctoral scholar in the Department of Plant Science. In return, the plant provides rhizobia with nutrients and a safe place to live. Like any complex biological phenomenon, this partnership is heavily moderated by interactions between the partners.
