Owners: Callum, John and Adrian Wesley
Location: Southern Cross, Western Australia
Farm size: 8000 hectares
Enterprises: 50 per cent cropping; 50 per cent cattle stud
Average annual rainfall: 315 millimetres, with a shift from winter to summer rainfall
Soil types: heavy red loam, red sands
Cropping program: wheat, barley, oats, chickpeas and lupins
Callum Wesley is among many grain growers facing environmental conditions that call for wheat varieties with a different set of early growth characteristics.
Callum faces persistent changes in rainfall patterns that can drench his paddocks over summer but leave the topsoil dry by sowing time (and also over winter). The new rainfall pattern has made it difficult to get a decent break for the past three seasons.
“The frustrating thing was detecting plenty of soil moisture in the soil profile at about 120 millimetres deep, but not being able to sow that deep with existing varieties.”
He reached breaking point in 2020, a year that delivered an exceptional 150mm of rain in February but no follow-up rain until late May. He knew, however, that CSIRO pre-breeders had developed wheat lines that could be sown deeper, right down to where his soils contained moisture.
These lines were developed by Dr Greg Rebetzke and his team by swapping out the commonly used dwarfing genes that were found to also slow the seedlings’ early growth. They were replaced with dwarfing genes that reduce crop height but allow seed to produce a much longer coleoptile and, therefore, an emerging shoot that can establish well, even when sown deep at about 100mm. Wheat lines containing the longer coleoptile trait have not yet been commercially released but are being progressed by breeding companies.
Callum contacted Dr Rebetzke over the Anzac Day long weekend in 2020 during the national COVID-19 lockdown to request seed for an on-farm trial. Designing and running the trial remotely with Dr Rebetzke was not an issue, as both have research and development experience.
The problem was a lack of seed: “I wasn’t planning on running a long coleoptile trial in 2020, which meant I had not bulked-up any seed,” Dr Rebetzke says. “That, however, did not stop Callum. He was like an attack dog. So, I collected and cleaned up every bit of seed carrying the trait. But it was several years old and we were taking a chance that the older age of the seed could affect seedling emergence.”
With only 100 kilograms of seed available, Callum had to modify his planter, including manufacturing a hopper to handle the small quantities, a feat he pulled off with his uncle, Adrian. He then managed to use the commercial-scale machinery to sow a small scheme of carefully controlled strips.
The trial was sown dry on 4 May at a depth of 100 to 120mm, and at 30 to 40mm for the controls not containing the long coleoptile trait. Ten lines containing the long coleoptile trait were tested against three commercial varieties as a control, including Mace (PBR).
Callum reports that the long coleoptile lines successfully germinated on summer water deep in the soil profile. They germinated unimpeded and gained a three-week head start in the warm autumn soils compared to the shallow-sown controls.
“Those extra weeks of growth meant the long coleoptile lines got extra rooting length and continued to access moisture deeper in the soil,” Callum says. “That head start also helped to mitigate against heat and drought stress in September and October.”
Between May and October, the trial site received 85mm of in-crop rain, ranking the season among the lowest for rainfall. However, the long coleoptile lines proved their worth, producing a crop with heads full of ripened grain at a time when the shallow-sown controls were struggling to fill grain.
“I’m looking at an overall yield of about 1.2 tonnes per hectare with the long coleoptile lines sown deep when I have a season to chase summer rain. For me, that makes for a much needed risk management tool and would amount to a profitable crop despite a horrible season.”
Callum has used the harvested seed to repeat the trial in 2021 to further explore gene-by-environment benefits from CSIRO’s alternative dwarfing genes. Dr Rebetzke, who continues to collaborate with Callum, says uptake of these genes by breeding companies has been strong and the genes are due to appear in commercial varieties over the next five years.