A powerful new tool is being developed to analyse the impact of wheat varieties’ disease resistance on crop performance to help growers select the best variety and management strategies to optimise yield potential.

The project, led by the Western Australian Department of Primary Industries and Regional Development (DPIRD) with co-investment by GRDC and several other contributors, is developing a ‘yield loss to disease’ tool that draws on five years of Australian field trial data and statistical analysis. It will be used to determine likely yield responses to various disease loads for wheat varieties with different resistance and tolerance ratings.

A prototype was unveiled at the GRDC Research Update in Perth in February 2020 for interested parties to test and provide feedback, so the new tool can be refined and expanded to barley before an official release next year.

Variety disease ratings are expressed as susceptible to very susceptible (SVS), susceptible (S), moderately susceptible to susceptible (MSS), moderately susceptible (MS), moderately resistant to moderately susceptible (MRMS) or moderately resistant (MR).

The Yield Loss to Disease Model presents the results in the form of a graph of a yield response curve, illustrating the amount of yield lost as a result of the interaction between disease pressure and variety resistance for a selected disease. A corresponding table is also produced, summarising the estimated yield loss in tonnes per hectare and percentage for selected resistance classes.

Model set for expansion

DPIRD biometrician Karyn Reeves says the prototype is configured to five wheat diseases – stem, leaf and stripe rust, yellow spot and nodorum blotch. The model will be expanded to a total of eight foliar diseases of wheat and barley, which will be available on GRDC's website later this year.

“The model has been developed so growers and consultants can make more-informed decisions about variety and paddock selection, by being able to compare the likely yield responses to various resistance categories of individual diseases,” Dr Reeves says.

“For example, users of the model will be able to compare the yield response to leaf rust from the wheat variety Mace , which has an MSS rating, to that of Ninja , which has an SVS rating, in a paddock with a moderate disease pressure.

“In the past, growers had to guess what the yield loss to disease would be. Now, they can rely on scientific analysis to provide the most likely outcome.”

Dr Reeves says the model clearly illustrates how influential a variety’s disease resistance rating is in determining yield performance in relation to disease pressure. “For example, a grower might expect to lose 30 per cent of the wheat crop’s yield to leaf rust for a susceptible variety, but only five per cent for a moderately resistant variety,” she says.

Multi-agency project

The Yield Loss to Disease Model is a collaborative project, with input from the New South Wales Department of Primary Industries, the Queensland Department of Agriculture and Fisheries, Agriculture Victoria and Statistics for the Australian Grains Industry (SAGI).

Dr Reeves says users can have confidence in the integrity of the data produced by the model, which was developed from a combination of scientific field trials and empirical data from across the country. “This is a very comprehensive project, which has involved a number of people providing data from trials across five states, as well as extensive statistical analysis to compile a robust product,” she says.

Cereal diseases have a significant impact on production, with wheat diseases alone costing the Australian wheat industry $468 million a year in lost yield and control costs. The Yield Loss to Disease Model can be accessed on the DPIRD website.

More information: Karyn Reeves, karyn.reeves@dpird.wa.gov.au; John Rivers, john.rivers@grdc.com.au