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Keep crown rot at bay


THE fungal disease crown rot is one of Australia’s most costly diseases in wheat, and with it generally doing most damage in years with dry springs, under the scenario of climate change it could foreseeably become an even bigger problem.

Yield losses from the disease, first spotted in the 1950s, can be up to 90pc in susceptible varieties, such as some lines of durum wheat, or 50pc, in bread wheats.

Looking to stop these losses, the Grains Research and Development Corporation (GRDC) has invested in a series of projects to minimise damage.

These projects cover pre-breeding, epidemiology, farming systems and pathology.

The GRDC also launched an extension program – Stop The Rot – in 2011.

Dr Jason Able makes a durum cross with an elite breeding line and a potential source of reduced crown rot susceptibility which has been provided through Dr Hugh Wallwork’s crown rot pre-breeding program at SARDI.

The campaign was designed to lift awareness of the need for a three-step program based on crop rotation, monitoring for basal browning as well as whiteheads in harvested grain and soil and stubble testing.

Crop rotation is a key method of stopping crown rot.

GRDC-supported research demonstrated that crop rotation reduces the incidence and severity of crown rot, resulting in average yield gains of between 17-23 per cent over continuous wheat rotations.

Precision planting techniques can also help.

NSW Department of Primary Industries research funded by the GRDC has also shown that inter-row sowing reduces the impact of crown rot and increases yield by up to 9pc in a wheat-on-wheat sequence.

Recent collaborative research between the Northern Grower Alliance and NSW Department of Primary Industries has also established that the presence of root lesion nematode (RLN) feeding within root systems increases the severity of crown rot.

This research highlights that cereal varieties differ in their tolerance to crown rot and RLN. This can have a significant impact on the relative yield of varieties in the presence of these various disease constraints.

In the heartland of crown rot, northern NSW, Garah grower Bill Yates emphasises the importance of rotations in controlling crown rot.

He says the cereal-legume rotations he and son Andrew have implemented have greatly reduced the incidence of crown rot in their wheat crops.

“The GRDC research results and the rotational changes we made as a result of them mean we are battling to find whiteheads (a key indicator of crown rot) now,” he said.

Mr Yates said it was quite rare now to plant wheat on wheat and only when crown rot levels had been measured and were a low risk.

But it is not just agronomics the GRDC has invested in.

It has committed funds to long-term genetics R&D to complement gains made through the adoption of recommended farm practices.

A range of new material is coming through breeding programs based on current commercial cultivars and recent additions to the set of crown rot resistance sources.

A new cereal research project began in 2013, aimed at boosting the resistance of durum wheat to crown rot.

This project aims to improve resistance in durum wheats by crossing them with hexaploid (bread wheat) and wild tetraploid wheats which carry good levels of crown rot resistance.

The national crown rot program is also focused on refining the PreDicta B ® pre-sowing test for this disease to enable growers to make more informed rotation and management choices before embarking on their cropping programs.

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