Australian researchers go head to head to tackle crown rot

Australia’s leading crop geneticists and disease researchers are going ‘head to head’ in a race to identify new germplasm that will allow cereal crops to yield well under crown rot pressure.

James Clark, Grains Research and Development Corporation (GRDC) northern panel chair, says growers will know by the end of the year if the major GRDC-funded project has been successful.

GRDC has funded research partners to develop wheat and barley lines capable of stable yield when grown in the presence of varying amounts of crown rot inoculum, Mr Clark said.

"Any material that is proven to yield under controlled conditions in the paddock will be given immediately to breeding companies,” he said.

"This will ensure that new varieties will become available to growers in the shortest time possible.”

This year, side-by-side comparisons of new germplasm, under controlled conditions with special statistical design, are being conducted at the University of Sydney’s I. A. Watson Wheat Research Centre at Narrabri, NSW.

Previous attempts to produce crown rot resistant varieties have been restricted by the necessity to achieve minimum standards in other traits such as stem rust resistance and high quality.

"It’s time to take a new approach and concentrate on adding different sources of crown rot tolerance and/or resistance to adapted germplasm, and get this out to growers as fast as possible.

"Stubble from previous crops provides an ideal substrate for crown rot to survive so under our northern farming system so it is unlikely crown rot can be eliminated.

"This means a genetic solution is the most appropriate way to produce varieties that can yield in the presence of the disease.

"Growers need access to varieties that are able to achieve high grain yield when grown under conditions that favour crown rot development, a good start with good nutrition and a hard finish.”

Mr Clark says the projects are closely linked and information and genetic material will be shared. They will tackle the problem of crown rot in different ways, to maximise the likelihood of successful outcomes for growers.

GRDC unveiled its investment at the PBI, Narrabri this week, including a managed environment facility (MEF) which will allow researchers to control the environment during trials in order to take a closer look at the effect of rainfall events, water use efficiency and nutrient management.

Mr Clark says there is no silver bullet to beating crown rot, but an integrated approach using genetics and management will enable growers to combat the disease and provide them with workable options.

Growers are reminded of GRDC’s previous research that advocates the ROT approach: Rotate crops, Observe plants for basal browning, and Test soil and/stubble for the presence of crown rot.

Collaborators include: the University of Southern Queensland (USQ); the University of Queensland (UQ); University of Sydney (SU); and CSIRO.

USQ has undertaken to provide useful markers that breeding companies can readily incorporate into their screening and selection regime.

These markers will indicate the presence of genes or gene combinations that resist growth of, or provide tolerance to, crown rot. They will make it easier to identify genes in breeding populations from crosses between enhanced lines and adapted varieties.

The UQ project seeks to rapidly move multiple genes conveying resistance/tolerance to crown rot into adapted, high-yielding genetic backgrounds of bread wheat.

A combination of technologies is being applied to rapidly move genes (from multiple sources) into bread wheat, including: ‘speed breeding’, (aimed at reducing the time taken from sowing to harvest to 12 weeks); high-throughput seedling and nursery screens to allow large population sizes to be evaluated for crown rot reaction; and use of advance molecular genetics tools to identify gene segments that contribute to crown rot resistance and/or tolerance.

Sydney University’s project has two components: one will focus on wheats adapted to the Northern Region and will use a recognised, although seldom used breeding strategy called Marker Assisted Recurrent Selection (MARS). The second component based in SARDI, South Australia, will focus on wheats adapted to southern and western Australia, and will also use molecular markers but will focus on more conventional crossing strategies.

CSIRO will look at known lines with different reactions to crown rot and cross these to adapted varieties from the three GRDC Regions to produce populations of plants that react differently in the presence of crown rot inoculum. These populations will be used to identify genes conferring crown rot resistance, and genes identified in mapping populations will be further validated in different genetic backgrounds under different field environments. The aim is to better understand how crown rot affects a plant as well as how a plant reacts to a crown rot infection.