Experimental and modelling studies of drought-adaptive root architectural traits in wheat (Triticum aestivum L.)

This paper presents an interdisciplinary approach to crop improvement that links physiology with plant breeding and simulation modelling to enhance the selection of high-yielding, drought-tolerant varieties. In a series of field experiments in Queensland, Australia, we found that the yield of CIMMYT wheat line SeriM82 ranged from 6% to 28% greater than the current cultivar Hartog. Physiological studies on the adaptive traits revealed that SeriM82 had a narrower root architecture and extracted more soil moisture, particularly deep in the profile. Results of a simulation analysis of these adaptive root traits with the cropping system model APSIM for a range of rain-fed environments in southern Queensland indicated a mean relative yield benefit of 14.5% in water-deficit seasons. Furthermore, each additional millimetre of water extracted during grain filling generated an extra 55 kg ha-1 of grain yield. Further root studies of a large number of wheat genotypes revealed that wheat root architecture is closely linked to the angle of seminal roots at the seedling stage - a trait which is suitable for large-scale and cost-effective screening programmes. Overall, our results suggest that an interdisciplinary approach to crop improvement is likely to enhance the rate of yield improvement in rain-fed crops.