THE risks of heat stress affecting Western Australian wheat crop yields are growing on the back of rising average spring temperatures associated with changes in the State’s traditional Mediterranean climate.

GRDC western regional panel member, Greg Rebetzke.

Grains Research and Development Corporation (GRDC) western regional panel member, Greg Rebetzke, who is a senior principal research geneticist at CSIRO, said WA’s northern grainbelt was hit particularly hard by high spring temperatures in 2014 that slashed the yield potential of cereal crops.

“Balancing some of the heat stress risks to crop production in the western region are grower trends towards earlier sowing practices and a shorter average crop growing season while maintaining reasonable crop biomass and yield potential,” he said.

Dr Rebetzke said a new GRDC Hot Topic Heat stress in the western region (www.grdc.com.au/hottopics) included details of GRDC-supported heat stress research, management practices to reduce risks of heat stress and links to resources such as the Flower Power tool which helped predict wheat flowering times and local frost or heat stress risk in WA.

He said the research into heat stress included research at La Trobe University and CSIRO Agriculture to better understand the effects of heat stress on wheat anther development, with the aim of breeding more heat tolerant varieties.

The wheat anther, which houses the developing pollen, is particularly susceptible to high temperatures and other environmental stresses.

Heat stress tolerance

Dr Rebetzke said an additional GRDC-supported project, co-funded by the South Australian Grains Industry Trust (SAGIT) and also involving Australian Grain Technologies, was conducting research in a controlled environment at Roseworthy, in South Australia, to identify and quantify the level of heat stress tolerance in current wheat varieties, advanced breeders’ lines and exotic lines.

“This project is also using ‘gene mapping’ to genetically dissect and understand the key sources of heat tolerance identified to date, with the goal of developing molecular markers for plant breeders to use in selection of varieties for heat tolerance,” he said.

Dr Rebetzke said that in WA, research at the GRDC-funded Managed Environment Facility (MEF) – housed at the Department of Agriculture and Food (DAFWA) in Merredin – was helping to validate wheat drought tolerance and yield results from the controlled environment trials under a range of ‘field’ conditions.

“The MEF facilities, which are also set up at Narrabri and Yanco, both in NSW, can induce or reduce drought stress – using rain-out shelters, irrigation and temperature control – and assess variety performance under a range of sowing dates and induced conditions of heat stress severity and duration,” he said.

Agronomic practices to mitigate the risks of future heat stress incidences and severity include:

• Tactics to conserve soil moisture, such as no-tillage and stubble retention
• Fertilising at crucial crop development stages
• Timing sowing to reduce the impact of heat towards the end of the growing season

“Research in the mid-2000s showed application of nitrogen, phosphorus and potassium (as well as some micro-nutrients, such as zinc) could improve wheat crop growth under heat stress conditions,” Dr Rebetzke said.

Source: GRDC