Ground Cover South : Ground Cover 056 June-July 2005 - South
Soils 14 GROUND COVER JUNE/JULY 2005 Mobile DNA lab to diagnose soil health By HELEN OLSEN n A mobile laboratory is travelling around Victoria, testing the biological health of the state's soils. It is part of a Victorian government initiative, Our Rural Landscape, and has been operating since September 2004. Dr Pauline Mele, soil biology coordinator with the Victorian Department of Primary Industries, says the technology can be used to measure soil health more accurately. "Currently, we can work out many of the chemical and physical properties of soil, but not so much about the dynamic processes at a microbiological level," she says. "This technology will help us to determine a soil's fitness for plant production, and if important functions that contribute to a healthy soil are being carried out." The laboratory uses molecular markers to identify bacterial genes that indicate if processes such as nitrogen mineralisation, antibiotic production (which can suppress disease organisms) and phytohormone production (which can stimulate root growth) are occurring. A major advantage of the laboratory being mobile is it enables the testing of soil samples on site, which eliminates the problem of sample deterioration that can occur during transport. Dr Mele explains that her team is taking a 'nested' approach to assessing soils. "Firstly, we want to ensure that the technology can be used to differentiate between the representative soil types, such as calcarosols and dermosols," she says. "Then we want to be able to assess the effects on soil health of different land uses such as crop/legume use, native pasture or remnant vegetation, within each soil class, "Lastly, we would like to compare the effects on the soil of different land management options, including fallow versus cultivation and organic versus conventional." The laboratory may need to add more target genes to its list to be able to carry out all these assessments. This is likely to involve collaboration with researchers at the University of California, who have developed gene- detecting techniques, Dr Mele says. Another aim for the laboratory is to attract young people into agricultural studies. "Many young people studying microbiology go into the biomedical field, she says. "This laboratory uses state-of- the-art technology, which we are hoping will attract students to soil science." For more information: Dr Pauline Mele/Andrew Oxley, 02 6030 4500; for a description of soil types go to www.grdc.com.au/growers/ oft/soiltype.htm Dr Pauline Mele: "This technology will help us to determine a soil's fitness for plant production." PHOTO: BRAD COLLIS SOIL KNOWLEDGE COMPILED organic carbon content on soil properties for some time. However, not much work has been done on the effects of different carbon fractions on soil properties, such as structure, colour, pH, and buffering capacity." The approach that the CSIRO Land and Water team is taking is novel because it focuses on the effect of carbon pools (particulate organic carbon and the humic fraction) on soil properties through field and laboratory studies and modelling exercises. These are used to predict changes in soil organic carbon pools over time. The humic fraction contains humus, an organic substance derived from partially or wholly decayed vegetable or animal matter. It is a rich source of nutrients for plants and increases the soil's ability to hold on to water and applied fertilisers. Team leader Jan Skjemstad says that although the report is written for academics, it will still provide important information for graingrowers. "It contains data that will allow us to advise growers and farmers on how to manage their soils to keep the properties that they wish to keep," Mr Skjemstad says. GRDC Research Code CSO00029 For more information: Dr Evelyn Krull, 08 8308 8516, firstname.lastname@example.org The report is available on the GRDC website www.grdc.com.au/growers/res_ summ/CSO00029/summary.htm By HELEN OLSEN n Current knowledge on the different components of soil organic matter and their influence on soil properties has been combined into a single review document for soils researchers and interested graingrowers. The document -- Functions of Soil Organic Matter and the Effect on Soil Properties -- has been compiled by researchers from CSIRO Land and Water in Adelaide for the GRDC and the CRC for Greenhouse Accounting. The review assesses current knowledge of the functions of soil organic carbon and its effect on physical, chemical and biological properties. Its senior author, Dr Evelyn Krull, notes: "People have looked at the effect of total BACTERIA PLANT GROWTH PUZZLE By REBECCA THYER n Re-inoculating healthy wheat plants with natural bacteria that live within the plant can promote plant growth and potentially boost grain yield, scientists at South Australia's Flinders University are discovering. Actinobacteria are found in soil and play important roles in decomposition and humus formation. But it is their role in promoting plant growth that is intriguing scientists such as biotechnologist and Grains Research Scholar Vanessa Conn. The Flinders University PhD student and her team have isolated actinobacteria from inside wheat roots and found that re-inoculating healthy wheat plants with the bacteria "actually promotes plant growth" while enhancing disease resistance. "At the moment we don't know how this is happening, and my role has been to understand the molecular mechanisms behind this interaction," Mrs Conn says. Any process that can boost growth promotion is obviously important to the grains industry, she says. "The rapid establishment of roots increases seedlings ability to anchor to the soil and to obtain water and nutrients from their environment, therefore enhancing their chances of survival and minimising the opportunity for pathogen infection." In the absence of disease pressure, the team also found that grain yield increases of five to 14 per cent were possible through re-inoculation, due to growth promotion activity. "Growth promotion compounds are often plant growth hormones and it was found that many of our endophytic strains are able to produce high levels of the plant growth promoter indole acetic acid (IAA)," Mrs Conn says. Additionally, re-inoculation causes the plant to turn on its defence system. "Plants have a way of defending themselves through a process called 'systematic acquired resistance' (SAR) or induced systemic resistance. "When a plant encounters a pathogen it activates a defensive pathway. Re-inoculating wheat plants ensures this defence pathway is switched on, meaning it has a better chance of warding off other pathogens." The process has been shown to work in the laboratory model plant Arabidopsis thaliana, a weed from the mustard family. And while a lot of work has been successful on this model, the next step is to isolate the compound responsible, Mrs Conn says. "If we can isolate that, it will really advance our work." Research work to find a successful biocontrol agent is proving to be difficult. "Our pot trials have been successful and now we are working on field trials." Mrs Conn finds understanding how plants operate an exciting task. "I wanted to go into research that had a clear focus or outcome. I did my undergraduate degree in biotechnology at Flinders University and decided to continue with my PhD here too," she says. "Eventually, I'd love to work overseas and continue my work in plant research. " GRDC Research Code GRS49 For more information: Vanessa Conn, 08 8204 8970, email@example.com Vanessa Conn.
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