A genetic solution to a disease that has troubled wheat growers for half a century may not be that far off.

Queensland Department of Primary Industries and Fisheries plant pathologist Damian Herde said wheat with greater crown rot resistance than any currently available would be provided to breeding companies in as little time as three years.

Dr Herde said it should then be possible to raise resistance levels in successive varieties, although total resistance might not be achieved.

He said the breakthrough in the Grains Research and Development Corporation-supported research had come from the crown rot team’s intensive screening of tens of thousands of plants a year in glasshouse and field trials.

As a result, the contenders had been whittled to six populations, all of which had strong crown rot resistance.

“The good news is that one has an advanced line related to EGA Wylie as a parent, which means enhanced resistance in a commercial variety could be available much sooner than using resistance found in wild relatives,” Dr Herde said.

“The best of the current commercial varieties, EGA Wylie and Sunco, have a crown rot resistance rating of 6.

“The resistant material we are working with is an easy 7, with resistance levels of 8 possible in successive varieties, 9 being the highest,” Dr Herde said.

He said crown rot was first formally recorded in Australian wheat in 1966 and had defied the efforts of plant pathologists and breeders for a varietal solution.

This was because of the complexity of the resistant genes and inheritance issues.

“The great challenge had been to combine increased crown rot resistance with agronomic characteristics that suit both those who grow and use the crop.

“The good thing, though, is that crown rot resistance is durable, meaning that a break-down of the resistance is unlikely,” Dr Herde said

He said disease management through rotating wheat with chickpeas, grain sorghum or millets, and using partially resistant varieties, was the industry mainstay to limit the effects of crown rot.

“This will change with the release of more-resistant varieties in years to come,” Dr Herde said.

He said crown rot was a major issue in the northern grain belt, cutting yields by up to 60-80 per cent in severe cases but more commonly by 20-30 per cent.

“It also has grain quality and downgrading implications through the production of small grain.

“Durum, the semolina and pasta wheat, is unfortunately highly susceptible to crown rot, as are some barley varieties,” Dr Herde said.

He said crown rot was caused by Fusarium fungi that built up in the soil in the absence of crop rotation, with disease symptoms becoming worse with a dry finish to the season.

The incidence of the disease had increased with the widespread adoption of the soil and moisture saving practice of reduced tillage, which provided ideal conditions for it to survive on crop residues.