Designing Crop Root Systems Efficient in Capturing Soil Water and Nutrients.

The current world-wide research on linking genes and root traits is focusing on the primary effects of genes that directly mediate small-scale phenomena such as the growth of meristems and specific uptake processes. However, the small-scale phenomena are of limited value in designing root systems for particular environments because much of the functional efficiency of root systems depends on large-scale phenomena, such as the 3-D distribution of root systems in soil, and how this distribution develops in time.

Simulation modelling plays an important role in understanding the spatial and temporal complexity of root-soil interactions at various scales. We have developed and used the 3-D model ROOTMAP that combines root structure and function with environmental cues to drive regulation on a whole-plant basis. It simulates water and nutrient dynamics (soil transport and plant uptake) and root growth responses to those dynamics in soils with varying resistance to root growth and differing water and nutrient supplies at scales ranging from micro (rhizosphere) to macro (field). We have documented that ROOTMAP (i) matches the patterns of root growth and nutrient uptake measured in the field and (ii) defines the optimal root structure and function regarding uptake of water, nitrate and P by lupins, wheat and field peas under variable seasonal conditions. We have successfully used ROOTMAP to (i) determine which root traits optimise plant performance in diverse environments, and (ii) express model parameters dealing with the root architecture in relation to genetic effects.