Traps help forecast disease
Blending old and new technology, SARDI researchers are advancing their understanding of pathogen spore release and climatic triggers
The development of molecular tests for pathogenic spores is enabling South Australian Research and Development Institute (SARDI) researchers to blend old and new technology to provide more detailed information about the relationship between spore release and climatic drivers.
Temperature and rainfall are known to trigger crop pathogens to release spores, which are then spread by air currents and rain splash. However, the impact of specific climatic conditions is hazy and how climate change may affect the prevalence or range of particular diseases is equally vague.
Automated spore traps have existed since the 1950s. They sample a known volume of air over a predetermined period of time. The air is drawn into the trap so that suspended particles and spores hit and stick to an adhesive tape mounted on a drum. This drum completes a full rotation in the predetermined time period, so that weather data can be linked to the time these spores were collected.
Traditionally, the particles that stuck to the tape were counted manually, a laborious process requiring expert ability to differentiate disease spores under a microscope. The demands of this work limited the number of traps used and the period of time being analysed.
Using the unique DNA fingerprint of each fungal pathogen, the team at SARDI led by Dr Alan McKay is developing techniques that allow the rapid and accurate detection of spores of key fungal diseases.
Following trials to validate the system, Dr Rohan Kimber from SARDI is using modified spore traps combined with the DNA assays to study the epidemiology of cereal and pulse diseases.
The spore traps are located at five sites in SA, from high-rainfall sites at Belair in the Adelaide Hills to the low-rainfall site at Orroroo in the Upper North.
“These sites represent a climate transect, as we want to establish the relationship between the release of spores by the pathogens and the climatic conditions they are responding to,” Dr Kimber says.
Each spore trap has an associated automatic weather station, which gathers temperature and rainfall data hourly, and four trays of trap plants.
“We have selected varieties that are susceptible to the disease of interest – yellow leaf spot in wheat, net form of net blotch in barley and blackspot in field peas.
“Surrounding each spore trap we place stubble that has been naturally infected with the disease of interest to provide a source of inoculum at each site.”
This study is supported by the SA Premier’s Research and Industry Fund and Transects for Environmental Monitoring and Decision-Making (TREND), and builds on a disease-management program funded by the GRDC.
“Our aim is to understand how these pathogens behave in different climatic zones and the patterns of spore release that occur.”
Between late autumn and early spring, trap plants are placed next to the spore trap each week at two sites. The trays of trap plants are brought to a glasshouse and placed in a humid chamber for four days to encourage the pathogens to grow. After three weeks, the plants are scored for disease symptoms to establish the rate of disease progression from a known spore release.
The theory is to quantify the spores released from the infested stubble captured by both the spore trap and the trap plants. The spore trap data generated using the molecular tests will be assessed and validated against the disease expression on the plants and correlated with the weather data.
“As we compile the spore release patterns for the different pathogens mapped over time we will look for correlations with weather conditions; eventually we would hope to be able to forecast disease outbreaks and provide growers with disease alerts, but this will not be an immediate outcome from this project.”
2013 is the final year of this three-year project, but Dr Kimber hopes to expand the trapping process into other growing regions. The timing will also be expanded to commence in February, to try to establish the influence of summer climatic conditions and the potential for early infection.
Dr Rohan Kimber, senior research officer, SARDI,
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