After close to 20 years of work, SA-based cereal pathologist Hugh Wallwork has made a breakthrough - successfully breeding crown rot resistance into well-adapted durum wheat lines.
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It could see durum wheat more likely to be grown again in lower rainfall areas such as the Murray Plains and the Mallee, where many farmers still have bad memories of crown rot causing scattered white heads in their crops and significant yield losses.
Crown rot is a soil-borne fungal disease.
Infection occurs on the crown and lower stems in damp soils. Moisture stress later in the season is the catalyst to the rot moving up the stem and causing browning and whiteheads.
"People that have been successfully growing alternative crops such as canola, lentils or chickpeas have been able to avoid crown rot by growing durum one year in four, but it is those ones that haven't had a suitable break crop from cereals that have gone away from growing it," he said.
Dr Wallwork, who was SARDI's principal cereal pathologist for 38 years, says when he started there was no durum breeding material with any crown rot resistance.
Even after retiring in 2022, he continued work on a voluntary basis at the University of Adelaide's Waite Campus, wanting to see it through to fruition.
"I knew if I didn't keep going with it that would be the end of it, after all the funding the durum growers had put in," he said.
Dr Wallwork says it has been a "long, slow process" crossing durum with bread wheats and wild durum, screening these plants and ensuring resistance is passed onto the next generation.
"Bread wheats had some crown rot resistance, but having a different chromosome number (to durum), there was a lot of sterility crossing them in the first few years," he said.
"We also used a wild-type durum which no one would ever grow because it was only about 20 per cent of the yields of current varieties."
He discovered the crown rot resistance was not just from one gene but multiple genes and while some early lines he developed showed promise, there were quality issues such as a lack of dough stability.
This changed in 2022 and 2023 when Dr Wallwork identified two lines, one with very good crown rot resistance and one with slightly lower resistance.
Both had yields similar to that of the Saintly variety, which is about 10-15pc below the best performing varieties such as Aurora.
These will go into AGT's stage two trials at five locations this year, including two in SA to be evaluated for yield as well as quality.
One of these could then be chosen for seed multiplication and commercial release.
Dr Wallwork is working on a small budget from the Southern Region Durum Growers Association and with in-kind support from SARDI and AGT.
He says an increase in funding to expand the populations being screened for crown rot resistance would speed up the process of finding a better commercial variety.
"Rather than this being the end, it is really just the start of delivering to growers, as there are likely to be some better lines coming through with better resistance and even better yields," he said.
"We saw one last year that showed greater promise, but it did not produce yellow enough flour for pasta production. We have however been using this as a parent for better lines going forward."
SADGA president Ethan Vogelsang, who has been growing durum for about six years at Padthaway, says the availability of varieties with good crown rot resistance could see the area durum is grown in expand into the higher rainfall zones too.
This could be assisted further by new seed dressing, Victrato, which offers crown rot resistance, likely to be available later this year.
