Grassroot trials to test long coleoptile wheat set  in motion a research investment that has broadened  to a multimillion-dollar national project

When Southern Cross grower Callum Wesley reached out to CSIRO plant geneticist  Dr Greg Rebetzke in 2020, he set in motion a research investment that has grown from an on-farm scale into a national project – and led to some practice changes along the way.

Mr Wesley was keen to trial the new long coleoptile wheat lines Dr Rebetzke and his  team were developing. These lines were potentially a better fit for the changing  rainfall patterns that he and other western growers faced.

The coleoptile is a protective sheath that encloses the emerging wheat shoot and first leaves. The longer the coleoptile is, the greater the emergence potential when deep sowing. Long coleoptile wheat can be sown at depths of more than 100 millimetres, making better use of stored soil moisture.

Soon an on-farm trial began, with Dr Rebetzke collecting every bit of seed carrying the trait and sending it to Mr Wesley.

Mr Wesley’s advocacy, and similar interest from other growers across WA, is credited for kickstarting further investment into agronomic and farming systems guidelines for long coleoptile wheat, including on-farm trials in the state’s northern and western regions and a newer $12.7 million national project.

GRDC sustainable cropping systems manager – west – Rowan Maddern, says the national project with CSIRO and its partners builds on previous work undertaken at national and regional levels to deliver a complete agronomic package to growers.

The long coleoptile work is an example of an issue raised by growers – arising out of local constraints and conditions – that has been picked up, ground-truthed as a National Grower Network (NGN) project in WA and scaled to a full national GRDC investment.

The four-year project is led by CSIRO, along with research parties including the University of Melbourne, NSW Department of Primary Industries and Regional Development, Queensland Department of Agriculture and Fisheries, SLR Agriculture, WA Department of Primary Industries and Regional Development, the University of South Australia and EPAG Research.

Dr Maddern says that to fully exploit the genetic potential of long coleoptile wheat, the relationship between genetic, environmental and management factors needs to be understood and optimised.

“This project pulls all variables together for seeding depth to give growers an agronomic package that they can pull off the shelf and apply when needed,” he says.

“It involves significant consultation with industry, including fertiliser and chemical companies and commercial breeders. The driving focus of this investment is to build on current work and collaborate with industry as a whole to benefit grain growers.”

On-farm trial adds questions

From Callum Wesley’s initial Southern Cross trials came the two-year NGN scoping study, and with that more questions.

In 2021, the private research, development and extension group SLR Agriculture set out to test the latest long coleoptile wheat varieties.

Based in York, 100 kilometres east of Perth, the scoping study generated great interest, with almost a thousand growers checking out the trials across two years.

Along with a similar project run in Queensland, it identified a suite of benefits that have helped inform the new GRDC-invested project, coordinated by Dr Rebetzke’s team at CSIRO, across all Australian growing regions.

SLR Agriculture CEO Michael Lamond says the scoping study also led to more questions because the trials not only deep-sowed the new long coleoptile wheat varieties but the conventional ones too – and it was their performance that surprised everyone.

Data from 2022 showed that Scepter and Mace emerged at rates of 70 to 80 per cent from 80 to 90mm deep.

SLR research agronomist Kate Witham, who leads the CSIRO research trials for SLR, says the early data has since been backed up by more recent work: 2024 data showed that in most trials there was 65 per cent emergence from sowing depths of 10 to 11 centimetres.

Mr Lamond says the results were “an absolute lightbulb moment” and showed how well conventional wheat could emerge from deep sowing.

Risks at depth

He says there have been concerns that chasing moisture beyond 50 to 60mm was a risk. “This is due to furrow fill from wind or rain significantly reducing the emergence percentage to a point where it impacts grain yield.

While trialling new long coleoptile wheat, SLR Agriculture found that deeper sown conventional varieties could emerge and generate reasonable yields, leading to on-farm practice change. Photo: Evan Collis

“That risk is still there,” he says. However, under warm soils with a dry profile above the seed, crop emergence is usually satisfactory.

Emergence can be very poor, though, if furrows are compacted from rain or filled in from a severe wind event.

SLR has two examples that show the risk or reward associated with these decisions. They come from the new, national CSIRO-led project.

Ms Witham says the worst-case scenario was at Kalannie this year (2024).

“Even though moisture around the seed at planting was sufficient for germination the soil was 28°C at 140mm below the surface.

“Seeding with a knife-point tyne caused soil disturbance, which when combined with warm daytime temperatures saw rapid water evaporation through furrows and no germination until season-breaking rains in June, 50 days later.

“Wheat had to then push through a heavy, wet profile to the surface. The plants that made it took an extra seven days compared  to those sown at 40mm.”

But there can be beneficial situations. At Dowerin, this year (2024), there had been similar climactic conditions to Kalannie,  but there were two differences at depth:  there was slightly more moisture, and it was cooler at 24°C.

“Varieties emerged 10 to 20 days later and by the break-of-season rains in May, deep-sown wheat was up and away,” Ms Witham says.

This is compared to dry/shallow-sown wheat, which was only just germinating and subject to 20 to 30mm furrow infill from heavy rain.

“That was the same story from Muntadgin, Corrigin and Buntine 2024 trials.”

Reasonable yields push practice change

While emergence was never as good as the long coleoptile varieties, “we often saw a reasonable enough strike that would get reasonable yields”.

Ms Witham says data backs this up. Nearly 300km east of Perth, at the Muntadgin site, Scepter^A yielded 2.2 tonnes per hectare when sown at 10cm, and 2t/ha at 4cm in 2023.

It is the same story for Calibre, which has a long coleoptile, and Denison a slow spring variety. Calibre had a 70 per cent emergence rate from depth and yielded 3t/ha, compared to 2.7t/ha when sown shallow with 100 per cent emergence. Denison so had a 70 per cent emergence rate from depth and yielded 2.8t/ha, and 1.9t/ha when sown shallow.

Mr Lamond says that it has prompted growers to try, which will assist in facilitating new variety adoption when the long coleoptile lines become available.

Dr Rebetzke says good emergence with conventional varieties depends on varieties and soil types. “The GRDC-supported project is exploring how soil factors, including how hard the soil is and soil moisture, will affect different existing varieties in their ability to emerge when sown to depths of 80 to 90mm. SLR’s data and insights have really driven the opportunity for WA growers on sandy soils, but we need to confirm there is similar opportunity across  the heavier textured soils in southern and eastern Australia.”

More information: $12.7m project for long coleoptile wheat.