Ground Cover Supplement : GC Supplement - Innovation and technology
GROUND COVER INNOVATION AND TECHNOLOGY 16 DISEASE Early detection of airborne disease DNA-BASED TESTING OF SOIL AS WELL AS AIR AND WATER IS CHANGING THE WAY THAT SCIENTISTS AND FARMERS CAN MAKE DECISIONS ABOUT PLANT DISEASE BY EMMA LEONARD aN eaRLY-WaRNING sYsteM for endemic and exotic disease pathogens would provide management and biosecurity advantages to australian graingrowers. Bonny vogelzang, a PhD student with the cooperative Research centre for National Plant Biosecurity, is developing and testing such a system under the supervision of Jenny Davidson of the south australian Research and Development Institute (saRDI) pulse and oilseed pathology group, Kathy Ophel-Keller of saRDI and eileen scott of the University of adelaide. New and old technologies have been combined to create an innovative method of early detection. Over the past five years, Jenny Davidson and colleagues at saRDI have used trays of pulse plants to trap airborne pathogens. the system has worked well but has limitations relating to timeliness, logistics, labour demand and the range of diseases and number of samples that can be processed. In discussions with pathologists from the UK, an idea for a revolutionary new system for collecting airborne pathogens was hatched. the system brings together the use of automated spore traps and DNa-based testing. automated spore traps have existed since the 1950s. these traps sample a known volume of air over a predetermined period of time. air is drawn into the trap and strikes an adhesive tape mounted on a drum, which completes a full rotation in the predetermined time period. any airborne particles stick to the tape, which is removed and analysed. traditionally analysis meant many hours of microscope work, carried out by experts able to differentiate between pathogens and pollen grains and between spores of different fungal species, such as Ascochyta rabiei and botrytis, for example. the demands of this work limited the number of traps used and resulted in only sections of the tape being analysed. however, each fungal pathogen carries a DNa signature that can be used to distinguish it from other organisms. this means molecular diagnostics can be used to identify the DNa of different pathogens and to quantify the amount of the pathogens present. such tools have recently been applied to spore trap samples and used in epidemiological studies in the UK. the potential to apply these tools for early warning surveillance for crop pathogens will be tested by the saRDI scientists. For her experiments, Bonny vogelzang has two spore traps located in sa, in association with comprehensive weather-recording stations. these gather data on daily rainfall, maximum and minimum temperature, relative humidity, wind speed and direction, soil temperature and leaf wetness. Weather-station data can be cross- referenced with the pathogen data to indicate conditions when pathogen spores are released. traps can be set to sample over 24 hours or seven days. the molecular diagnostic tools have the ability to identify extremely low levels of pathogens; potentially only one spore needs to be present. Ms vogelzang’s study is focusing on three fungal pathogens – blackspot (field peas), blackleg (canola) and Ascochyta rabiei (chickpeas). she is using these three pathogens as models, to establish the minimum aerial concentrations of spores able to be detected by the spore-trapping system using molecular tools. “Data from the project will help improve our understanding of the dispersal of these diseases in relation to weather conditions and will be used to further validate the diagnostic tools and disease prediction models,” Ms vogelzang says. “accurate early detection of disease pathogens will mean growers can anticipate crop-protection requirements, improving timeliness of operations and potentially reducing the use of insurance applications of fungicides.” Prediction models such as Blackspot Manager and Blackleg sporacle (both accessed at www.agric.wa.gov.au/cropdiseases) provide growers with valuable tools for identifying the risk of these diseases in their region before seeding. combining the two technologies has the potential to provide pathologists and quarantine agencies with the ability to identify new pathogen incursions that could threaten crop production. In addition to using molecular tools to identify specific disease pathogens, Ms vogelzang is also conducting research into DNa-fingerprinting tools which produce a DNa profile of all the fungal species in a sample. she is applying this technology to see if it is possible to detect when a new fungus is present in air samples. this technique does not rely on prior knowledge of the DNa signature of the new fungus, and so is potentially a very valuable technique for detecting unanticipated new pathogens. this system, known as ‘community profiling’, has never been used on air samples. If it works it will provide a substantial improvement in the early detection of exotic fungal pathogens. GRDc is a core participant in the cRc for National Plant Biosecurity. More information: Bonny Vogelzang, 08 8303 9390, email@example.com "Data from the project will help improve our understanding of the dispersal of these diseases in relation to weather conditions"
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