THE benefits of early sowing have been proven across many seasons, including this one, with many of the state's earlier-sown crops faring better than those sown later.
But an issue with early sowing can be accessing adequate moisture to ensure good crop establishment.
CSIRO research, supported by the GRDC, is investigating the use of genes that increase the length of a plant’s coleoptile – a protective sheath enclosing the shoot tip and first leaves of wheat.
Seed that germinates with long coleoptiles can be sown deeper in the soil to make use of residual moisture left over from summer rains. This means plants with long coleoptiles are potentially better suited to capturing the yield benefits associated with early sowing than plants with shorter coleoptiles.
CSIRO wheat geneticist Greg Rebetzke said about 50 years ago there were wheat varieties with good potential for early sowing, due to their long coleoptiles.
But with the green revolution and the introduction of dwarf varieties, the coleoptile length was also shortened.
“The dwarfing genes reduced the height of the crops, so as the plants were made shorter, the size of the coleoptiles was reduced,” he said.
Dr Rebetzke said, at the moment, it was not recommended to sow unless there was sufficient moisture in the top five to eight centimetres of the soil profile, otherwise poor emergence was a strong possibility. This led growers to delay sowing, which could result in yield penalties.
But, CSIRO research could enable farmers to sow at depths of up to 12.5 centimetres, reducing the reliance on the moisture in the soil’s upper level. This ability to chase moisture deeper in the soil profile would not compromise the ability of the crop to establish strongly.
To do this, researchers have identified dwarfing genes that could reduce crop stature without reducing coleoptile length and early growth.
CSIRO researchers have also identified genes that actively promote coleoptile length.
Plants with the desired combination of genes to promote longer coleoptile length have been passed onto breeding companies to validate in their own programs.
“Breeding programs in Australia are so efficient, but they often focus on aspects like quality and disease traits,” Dr Rebetzke said.
“Pre-breeders can do more exploring outside those constraints, with other genes that might be useful for Australian growers.
“Australian wheat breeders now have new genes that can produce a wheat plant the same height as varieties such as Mace but that have a longer coleoptile of up to 12.5cm in length that can access water stored deeper in the subsoil.”
Dr Rebtezke said given the increasingly variable rainfall experienced across the nation, new technologies and crop varieties that made better use of any available rainfall would be critical for Australian farming systems.
“By being able to sow at the right time, and crops being able to access deep moisture, it could save farmers money by minimising the risk of having to sow again,” he said.
Frost work
As well as exploring how farmers can proceed with earlier sowing confidently, CSIRO researchers are also looking at ways to get around a major issue for the state – frost.
Large tracts of the state’s cropping area have been wiped out by frost this year, leading many farmers to cut for hay, and others with few options.
CSIRO wheat geneticist Greg Rebetzke said researchers were working on developing awnless varieties, which could offer growers some options in years when frost hits.
“A major part of the GRDC’s five-year strategic plan is to build productivity and profitability for Australian growers,” he said.
“Frost is a major challenge and we’re working on options to try and help growers improve their capacity to deal with frost.
“It may not be developing tolerant varieties, but looking at other options like grazing or cutting for hay, so you haven’t burnt all the money on the crop.
“With the frost window widening, we need to look at all the options. Developing frost tolerant varieties is a challenge but there are other ways we can help growers.”
Other areas that the CSIRO were concentrating on included improving the water use efficiency of crops, as well as increasing weed competitiveness, a growing need with herbicide resistance on the rise.
“We’re focused on delivering outcomes for growers, not just undertaking science for science’s sake,” Dr Rebetzke said.
