Biological nitrification inhibition (BNI)-Is there potential for genetic interventions in the Triticeae?

Abstract

The natural ability of plants to release chemical substances from their roots that have a suppressing effect on nitrifier activity and soil nitrification, is termed 'biological nitrification inhibition' (BNI). Though nitrification is one of the critical processes in the nitrogen cycle, unrestricted and rapid nitrification in agricultural systems can result in major losses of nitrogen from the plant-soil system. This nitrogen loss is due to the leaching of nitrate out of the rooting zone and emission of gaseous oxides of nitrogen to the atmosphere, where it causes serious pollution problems. Using a newly developed assay system that quantifies the inhibitory activity of plant roots (i.e. BNI capacity), it has been shown that BNI capacity is widespread among crops and pastures. A tropical pasture grass, Brachiaria humidicola has been used as a model system to characterize BNI function, where it was shown that BNIs can provide sufficient inhibitory activity to suppress soil nitrification and nitrous oxide emissions. Given the wide-range of genetic diversity found among the Triticeae, and the current availability of genetic tools for moving traits/genes across members, there is great potential for introducing/improving the BNI capacity of economically important members of the Triticeae (i.e. wheat, barley and rye). This review outlines the current status of knowledge regarding the potential for genetic improvement in the BNI capacity of the Triticeae. Such approaches are critical to the development of the next-generation of crops and production systems where nitrification is biologically suppressed/regulated to reduce nitrogen leakage and protect the environment from nitrogen pollution.