Ground Cover Supplement : GC Supplement - Collaboration
9 COLLABORATION GROUND COVER SOIL & WATER A DNA METHOD DEVELOPED in a project studying soil biology and pasture productivity is now assisting cereal breeders in their search for germplasm with improved drought tolerance. The high-throughput DNA extraction system for soil, developed by the South Australian Research and Development Institute (SARDI) and CSIRO, can be used to measure living cells of any organism in a soil sample. Quantitative assays allow determination of the density of multiple target organisms in a 500 gram soil sample. These target organisms can include plant roots, soil-borne pathogens and beneficial soil microbes. This revolutionary method of rapid soil analysis was launched more than 10 years ago. It has been widely used by growers, agronomists and researchers to assess the risk of soil and stubble- borne plant pathogens such as rhizoctonia, cereal cyst nematode, take-all and crown rot. In a co-investment project between Meat and Livestock Australia, Australian Wool Innovation and the GRDC, DNA assays were developed to measure common pasture pathogens including pythium and phytophthora. In addition, assays were developed to measure beneficial organisms such as arbuscular mycorrhizal fungi and Trichoderma spp., as well as plant root systems. While cereal root systems can be relatively easily isolated and observed, the roots under a mixed pasture sward are an intertwined mass. Assays sufficiently sensitive to identify one milligram of a specific plant root in 500g of soil were developed for six common pasture species -- lucerne, phalaris, ryegrass, subterranean clover, barley grass and silver grass. Results from pot trials using ryegrass showed that changes in plant DNA in the soil are more rapid than changes in root dry weight. These results highlight the usefulness of DNA assays in measuring changes in root growth over current standard practices of washing out and weighing roots. These results led to the DNA technique being used for research on the root architecture of wheat, barley and canola in a project funded by the GRDC and the SA Grains Industry Trust (SAGIT). In the search for plants with improved water use efficiency or greater ability to withstand attack by soil pathogens, scientists have been using a range of methods to record and measure roots. While a DNA assay does not provide a structural picture of the root system, it does provide a method of rapidly quantifying how much root material is present in soil samples collected from different depths in the soil profile. The successful application of the DNA technique in these trials led to a research collaboration between plant breeder Dr Jason Eglinton, from the University of Adelaide, and the team at SARDI. Dr Eglinton wanted to establish if the DNA method could differentiate barley varieties with known differences in root distribution. The success of the barley root distribution research led to a collaboration with Australian Grain Technologies (AGT) to assess wheat lines grown at eight trial sites across SA as part of research on drought tolerance. The results found that the greatest differences in root mass were in the top 10 centimetres of soil. Most importantly it was found that the differences had a strong genetic basis. This suggests that root architecture can be bred for and that DNA assays may provide plant breeders with a useful tool for rapid assessment system of roots in their search for more drought-tolerant germplasm. □ GRDC Research Code DAS00075 More information: Dr Alan McKay, SARDI, 08 8303 9375, firstname.lastname@example.org ROOT ANALYSIS Sometimes the results of collaboration can be quite unexpected By Alan McKay DNA assays provide a method to rapidly quantify root systems. A DNA ASSAY CAN RAPIDLY QUANTIFY HOW MUCH ROOT MATERIAL IS PRESENT IN SOIL. TEAM LEADS THE WORLD IN SOIL TEST DEVELOPMENT DNA technology has come a long way since 1997 when SARDI launched the Root Disease Testing Service (now marketed as PreDicta B®) to quantify a range of soil-borne root diseases of cereals. The team is now very experienced at developing assays that work well in soil and leads the world in this area. This technology has benefited the grains industry in Australia, and expanded to develop tests for soil-borne pathogens of potatoes and pastures, as well as finding a use in environmental monitoring of aquaculture. Over the past 10 years investors in the development of this technology have included the SA Grains Industry Trust, Meat and Livestock Australia, Horticulture Australia Ltd, Australian Wool Innovation, Bayer CropScience and the GRDC.
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