Wheat growers who have struggled with dry conditions across vast tracts of Queensland and New South Wales during the winter cropping season, will be heartened to know research is underway to develop new genetics for wheat varieties that make better use of precious and increasingly variable rainfall.
Long-term research investments by the Grains Research and Development Corporation (GRDC) in partnership with the CSIRO are investigating the development of genes that increase the length of the coleoptile, a protective sheath enclosing the shoot tip and first leaves of wheat.
Seed which germinate 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 yield benefits associated with early sowing than plants with shorter coleoptiles.
CSIRO wheat geneticist Greg Rebetzke leads this research and said his team was committed to delivering traits and germplasm for improving crop variety’s water use efficiency, as well as weed-competitiveness.
The research team has a close working relationship with commercial plant breeders to understand the benefits of one trait over another and how to integrate new genetics into the development of higher-yielding, more robust cereals.
"Drought commonly limits productivity of Australian wheat crops. This research is about delivering ‘more crop per drop’ so grain growers can get maximise benefit from rainfall, as well as contributing to the breeding of new wheat lines that are more weed-competitive," Dr Rebetzke said.
"This year after what was a relatively limited winter crop planting many growers in Queensland and NSW experienced very dry conditions, which made it difficult for crop seeds to access the moisture located deep in the soil.
"Given the increasingly variable rainfall, technologies and crop varieties that make better use of rainfall will be critical for Australian farming systems."
As part of this research investment CSIRO researchers have identified new, alternative dwarfing genes that could potentially reduce crop stature without reducing coleoptile length and early growth, as well as genes that actively promote coleoptile length. The dwarfing genes are associated with reduced lodging when grown under conditions of higher nitrogen fertilisation.
These new parental germplasm shows considerable promise in breeding wheats with improved water-use efficiency, weed-competitiveness, and larger root systems/greater nitrogen uptake.
Plants with the desired combination of genes have now been passed on to wheat breeders to validate in their own programs, and then in the development of new long coleoptile varieties.
"Australian wheat breeders now have new genes that can produce a wheat plant the same height as varieties such as Mace or Yitpi,
but that have a longer coleoptile of up to 12.5cm in length that can access water stored deeper in the subsoil," Dr Rebetzke said.
Wheat lines incorporating these genes have undergone field testing at the GRDC’s Managed Environment Facilities throughout Australia and at the Central West Farming Systems’ Condobolin Agriculture Research and Advisory Station in NSW.
"We hope to learn more about these genes and be able to identify and release new wheat lines with the capacity to be sown as deep as 10cm - or even 12.5cm deep - if these new genetics are combined with improved technologies around planting equipment," Dr Rebetzke said.
Currently, wheat cannot be sown unless there is sufficient moisture within the top five to eight centimetres of the soil profile, or poor rates of emergence are a possibility. This caveat often causes growers to delay sowing past the optimal date, resulting in yield penalties.
"The new establishment trait is designed to allow growers to chase soil moisture deeper in the soil profile without compromising the ability of the wheat crop to establish strongly," Dr Rebetzke said.
"We also know that small increases in soil temperatures especially with earlier sowing can reduce coleoptile length. Together with some older seed treatment known to effects on coleoptile length, seedling establishment is one of the most risky periods for growers setting up their crops."
The coupling of new genetics and improved phenotyping has also allowed the development of weed-competitive wheat germplasm to be used as parents in the development of new varieties.
"The close engagement with commercial breeders throughout the extensive breeding effort is beginning to deliver large numbers of lines with their first yield assessments made during this season (2018)," Dr Rebetzke said.
"When coupled with appropriate agronomy, harvest weed-seed collection technologies and new chemistries, the potential for competitive wheats to control weeds and reduce costs to growers is in the making."
GRDC Grower Relations Manager North Richard Holzknecht said investment into cereal breeding for a changing climate was critical for grain growers.
"The challenges of this season in Queensland and NSW have just served to reinforce the importance and potential value on-farm of wheat varieties that make better use of rainfall and stored soil moisture," he said.
"The potential development of wheat variety that can be sown deeper into the soil to maximise use of soil moisture could become a game changer for growers, particularly with what seems to be increasingly variable weather patterns.
"Given the herbicide resistance issues becoming increasingly prevalent in Australia breeding wheat that is more weed-competitive will also be an invaluable tool in growers’ management strategies."
