Breeding more productive grain crops - could selecting the right rooting traits help?

Abstract

Root systems and their interactions with the below-ground environment are difficult to study. As a result, root research has typically lagged behind that carried out on above-ground parts of crop plants. Modern advances in computing technology are allowing 3D root architectural models to play a role in below-ground investigations. ROOTMAP is one such model, and has been used to investigate the influence that lupin root systems can have on water and nitrate distributions and nitrate leaching in field soils. Simulating a wide range of root architectures, ROOTMAP predicted that to reduce nitrate leaching to depth below lupin crops, a trade-off between surface and subsoil rooting density is required, with high rooting density in the topsoil alone insufficient to minimise leaching. Simulated plants that rapidly established a relatively high density of roots in the topsoil, reduced total nitrate leached with the break of season rains. Further increases in topsoil root density were, however, a poor investment of internal assimilates. A shift in resource allocation to subsoil root growth as the season progressed, gave plants a second chance to acquire nitrate previously leached to depth, and proved the most successful strategy for reducing total annual losses of nitrate. Given the ability to investigate rooting traits and quantify potential benefits of one rooting form over another, root modelling can be used to identify desirable root traits for which genotypes can then be screened. ROOTMAP is currently being used to investigate below-ground competition between wheat and annual ryegrass for both mobile (eg. water, nitrate) and immobile (eg. phosphorus) soil resources. This work will aid in the identification of key rooting traits that confer a competitive advantage to wheat.