How close are we to nitrogen-fixing cereals?

Engineering nitrogen-fixing cereals is essential for sustainable food production for the projected global population of 9 billion people in 2050. This process will require engineering cereals for nodule organogenesis and infection by nitrogen-fixing bacteria. The symbiosis signalling pathway is essential to establish both bacterial infection and nodule organogenesis in legumes and is also necessary for the establishment of mycorrhizal colonisation. Hence this signalling pathway is also present in cereals and it should be feasible to engineer this signalling pathway for cereal recognition of nitrogen-fixing bacteria. However, establishing a fully function nitrogen-fixing symbiosis in cereals will probably require additional genetic engineering for bacterial colonisation and nodule organogenesis.