Integrated root phenotypes for improved rice performance under low nitrogen availability

Ajmera, Ishan, Henry, Amelia, Radanielson, Ando M., Klein, Stephanie P., Ianevski, Aleksandr, Ben-nett, Malcolm J., Band, Leah R. and Lynch, Jonathan P. 2022. Integrated root phenotypes for improved rice performance under low nitrogen availability. Plant, Cell & Environment 45(3):805-822.

Greater nitrogen efficiency would substantially reduce the economic, energy andenvironmental costs of rice production. We hypothesized that synergistic balancingof the costs and benefits for soil exploration among root architectural phenes isbeneficial under suboptimal nitrogen availability. An enhanced implementation ofthe functional–structural modelOpenSimRootfor rice integrated with theORYZA_v3crop model was used to evaluate the utility of combinations of root architecturalphenes, namely nodal root angle, the proportion of smaller diameter nodal roots,nodal root number; and L‐type and S‐type lateral branching densities, for plantgrowth under low nitrogen. Multiple integrated root phenotypes were identifiedwith greater shoot biomass under low nitrogen than the reference cultivar IR64. Thesuperiority of these phenotypes was due to synergism among root phenes ratherthan the expected additive effects of phene states. Representative optimal pheno-types were predicted to have up to 80% greater grain yield with low N supply in therainfed dry direct‐seeded agroecosystem over future weather conditions, comparedto IR64. These phenotypes merit consideration as root ideotypes for breeding ricecultivars with improved yield under rainfed dry direct‐seeded conditions with limitednitrogen availability. The importance of phene synergism for the performance ofintegrated phenotypes has implications for crop breeding.