Long coleoptile wheat varieties show promise in trials

CSIRO have been developing the long coleoptile trait for more than 15 years and EP Ag Research director Andrew Ware said they had the foresight to realise it could be "revolutionary for Australian agriculture".

The coleoptile extends from the seed and acts as a protective covering for the first shoot during germination. A long coleoptile allows a seeding depth of up to 12 centimetres, compared with a traditional sowing depth of 3-5cm.

With a changing climate, CSIRO realised alternative seeding programs like deeper sowing could give fledgling crops access to previously inaccessible subsoil moisture for germination without having to wait for an autumn break.

"Being able to establish a crop a bit earlier into warmer soil allows roots to explore more of the soil profile through the growing season and that allows them to use moisture more efficiently," Mr Ware said.

"A sowing difference of just a couple of weeks, in some circumstances, can add nearly a tonne a hectare of yield so it does have the capacity to improve our chances of a profitable crop in more years."

In trials conducted on a sandy soil at Cootra, Mr Ware and EP Ag Research intern Rhaquelle Meiklejohn examined the performance of LC Mace (a LC derivative of Mace) against a standard Mace at different sowing depths. They also examined four commercial LC varieties - Valiant CL Plus, LR Bale, LR Dual and Calibre - at 4cm, 8cm and 10cm sowing depths.

Eleven days after seeding, the 8cm-sown LC Mace had established 44 per cent more plants than its traditional counterpart and 50pc more when sown at 10cm.

Six weeks after seeding, there was no difference in plant number, while yields from both varieties were the same from a 10cm sowing and the regular Mace performed better (4.56 tonnes a hectare to 4.17t/ha) at 8cm.

"We were hopeful they would be versatile enough that they'd yield as well as the more traditional cultivars when sowed shallower but that wasn't the case," Mr Ware said.

"Having said that, they're relatively new in their development and once more breeding goes into them, a grower may be able to choose a variety with a long coleoptile gene in it, allowing them to sow at a traditional depth or deeper if the season dictates to get a crop established at the right time."

In the commercial variety trial, there was no yield penalty when planting at 10cm (average yield of 3.62t/ha) compared with 4cm (3.49t/ha) and those planted at 8cm yielded the highest, averaging 3.75t/ha.

Dr Ware is excited about the potential of long coleoptile varieties and the impact they could have on the industry, but says there is more investigation to be done to find their best fit.

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He and Ms Meiklejohn are conducting more trials on the EP this year on more soil types and also trialling more commercial varieties as they are released.

"The 2021 trial was grown on a fairly friendly sand and they established really well," Dr Ware said.

"We anticipate this long coleoptile gene will really come into its own when we try it on heavier soils, because it will have the ability to push through from a deeper depth than what traditional cultivars can.

"The other thing we're trying to work through is the fact that a farmer might have 10 different soil types across a paddock and the moisture be at different levels so how do we identify that and how do we make sure we're sowing into moisture right the way across."

Dr Ware said LC varieties may not suit a disc seeding system where placement of the seed at different depths would be more difficult.

He said while LC varieties performed best when sown at 8cm during the 2021 trials, there wasn't a significant downside to sowing deeper.

"A lot of growers dry sow based on the calendar, but this gene allows the establishment of a crop by a calendar date and that's a dream come true," he said.

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