Quantitative DNA assays for measuring root distribution and seed banks in soil are under development for wheat, barley, ryegrass, subterranean clover, phalaris and lucerne. These assays have potential to determine root distributions in soil profiles in either monoculture or mixed sward systems. The assays quantify DNA from live cells only and many of these cells will be in fine roots, prone to loss during soil washing with conventional root assessment procedures. In pot experiments the ryegrass DNA assay showed a rapid decline in soil root DNA over 10 days following plants being either defoliated or sprayed with glyphosate. This response is most likely due to DNA degrading in dying root cells. DNA assays for wheat and barley have also been used to assess genetic differences in root architecture under drought conditions and at field sites with hostile subsoils. The assays for pasture species have been used to measure differences in root distribution of pasture species in lime amended plots at the MASTER site (NSW DPI, Wagga Wagga). Results from the above studies show that quantitative DNA assays combined with high throughput DNA extraction systems are potentially useful to determine distribution of root systems under field conditions. This paves the way for high-throughput root phenotyping and incorporation of root architecture traits into breeding programs to improve drought tolerance as one possible role for the technology. In pasture trials the assays have the capacity to measure the impact of different management systems on specific species in mixed swards.Alan McKay, Ian T. Riley, Di Hartley, Sue Wiebkin, Herdina, Guangdi Li, Stewart Coventry, Sharla Hall, and Chunyuan Huan
