Modern wheat has deeper roots than ancient wheats: is this an adaptation to higher productivity?

There is growing interest in the production of ancient grains including emmer, einkorn and spelt, particularly in low-input systems. Differences in their root systems and how these affect water and nitrogen uptake are not well known, but can offer important insights into the effects of plant breeding on resource use and root physiology, which can inform breeding of future crops.

In this study, we used imaging in minirhizotron tubes to evaluate root development in emmer, einkorn, spelt and modern wheat growing under field conditions, taking images to 2.2 m soil depth. We evaluated water stress in the different species using carbon isotope discrimination and used a nitrogen tracer to compare N uptake over time.

The results show that modern wheats have deeper and more efficient root systems. Modern wheats showed less water stress in late developmental stages due to their deeper roots which allow access to deep soil water, and can therefore sustain high grain yields. They were also able to translocate N more efficiently to the grain. The results contradict previous hypotheses that modern wheat has shallow rooting systems due to high inputs, showing that where more nutrient resources are available, deeper roots have become important for water uptake to support higher yields.

This is the first field study of roots of ancient and modern wheats, where we clearly see that there are substantial differences between the root systems. These results help to explain how past selection for yield has affected below-ground crop physiology.