Time is right to test for damaging soil pathogens
Author: Melissa Williams | Date: 21 Dec 2017
PREDICTA® B is the grains industry’s ‘go-to’ DNA-based soil testing service to identify pathogens posing the greatest risk to cereal crops - and summer is the ideal time to use it to assess what is in your soil.
Stemming from Grains Research and Development Corporation (GRDC) investments, PREDICTA® B is provided by the South Australian Research and Development Institute (SARDI), a division of Primary Industries and Regions SA (PIRSA).
Dr Alan McKay, the leader of SARDI’s Soil Biology and Molecular Diagnostics group, was recently in Perth for a PREDICTA® B Root Disease Risk Management Course.
He said PREDICTA® B can measure the levels of - and assign disease risk categories for - pathogens that cause: rhizoctonia root rot, crown rot, take-all, a range of root lesion nematodes (RLN) and cereal cyst and stem nematodes.
The test can also quantify - but not yet assign disease risk ratings for - pathogens that cause: common root rot, Pythium clade, eyespot, charcoal rot; ascochyta blight (chickpea), yellow leaf spot and white grain disorder of wheat.
“Many of these diseases have been identified as ongoing, increasing or emerging issues in the western region, Dr McKay said.
“PREDICTA® B is an important tool to help diagnose and manage these and reduce risks of significant crop losses in subsequent seasons.
“But it is best to liaise with an accredited adviser when taking soil samples, interpreting and understanding PREDICTA® B results and developing a plan for variety, rotation and paddock management decisions for next season.”
Soil and root testing is also carried out during the winter crop growing season by the Department of Primary Industries and Regional Development (DPIRD) Diagnostic Laboratory Services (DDLS) in South Perth.
Dr McKay said RLN found in WA could reduce grain yields by up to 50 per cent and testing showed half of the State’s affected paddocks had RLN at yield-damaging levels.
“Previous PREDICTA® B testing in WA has identified significant areas of the State – from Geraldton to Esperance – that are at risk of crop damage from the RLN species Pratylenchus neglectus and P. quasitereoides (P. thornei has been detected in only a low number of soil samples),” he said.
‘It is important to know which species of RLN are present in your soil because different crops and varieties vary in tolerance
(performance under pressure of RLN) and resistance (genetic susceptibility) to each of the nematode species.
“Rotations and variety choices that control one species of RLN may not effectively control another.”
Dr McKay said crown rot was another damaging soil pathogen found in WA and summer soil testing could help to plan crop rotations and varieties to reduce the risks of this disease, which could cut wheat and barley yields by almost 20 per cent.
“Caused by the fungus Fusarium pseudograminearum, F. culmorum or F. graminearum, the state’s ‘hot spot’ for crown rot is the eastern grainbelt,” he said.
According to research led by DPIRD research officer Daniel Hüberli, with GRDC investment, yield losses from crown rot are highest when there is a hot, dry spring finish to the growing season and all cereal crops can be affected.
He said in a wet spring finish, disease inoculum levels in the soil would still increase after cereals, even when there were no typical whitehead symptoms expressed in-crop.
Dr Hüberli said through the DPIRD ‘Boosting Grains R&D Project’ in 2017, he had found some oats were behaving similarly to wheat and barley under crown rot pressure.
“I have seen yield losses of about 8 per cent in preliminary trials and it appears oats are not a good break crop option in high risk crown rot paddocks - as all varieties tested appear to increase inoculum,” he said.
Caused by the fungus Rhizoctonia solani AG8, rhizoctonia root rot is a widespread soilborne disease that also impacts on both cereal and lupin crops across the WA grainbelt in most seasons.
Its main hosts are cereals and grass weeds and it can lead to grain yield losses of up to 50 per cent in severe cases. Barley is typically more susceptible to rhizoctonia than wheat in WA, while oats are less susceptible than barley and wheat.
“If a paddock was suspected of having this disease in 2017, or there is a history of bare patches, testing using PREDICTA® B is valuable to help determine rhizoctonia levels and risks for 2018 and to develop a management plan,” Dr McKay said.
At the 2018 GRDC Grains Research Update, Perth, DPIRD researchers will provide further updates of latest research, development and extension (RD&E) into RLN, crown rot, rhizoctonia and other soilborne diseases specifically for the western region.
This event is scheduled for February 26-27 at Crown Perth and registrations are open at www.giwa.org.au
Growers and advisers can find out more about PREDICTA® and their nearest accredited consultants by contacting Dr McKay on 08 8303 9375 or firstname.lastname@example.org. More information can also be found at http://pir.sa.gov.au/research/services/molecular_diagnostics/predicta_b
The PREDICTA® B laboratory is closed for an extensive renovation, but is expected to be operational in early February 2018. Soil samples can be submitted before this and will be stored until processing recommences.
Dr Alan McKay, SARDI
08 8303 9375
Natalie Lee, Cox Inall Communications
0427 189 827
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