Many northern sorghum growers are concerned about the increasing frequency of high heat days in the region. Temperatures above 38 oC can damage the viability of sorghum plant pollen, which leads to decreased seed production and reduced yield.
With support from GRDC and the Department of Agriculture, Queensland researchers have discovered the potential to develop new sorghum varieties that are adapted to increased temperatures.
Scientists from CSIRO and the Queensland Alliance for Agricultural and Food Innovation (QAAFI) at The University of Queensland (UQ) have demonstrated that some sorghum varieties are more sensitive to heat than others. Sorghum lines susceptible to temperatures of 38oC were only able to retain five per cent of their grains, while others retained 60–70 per cent.
Professor Graeme Hammer, who leads the QAAFI team, says the discovery means commercial breeders could be developing ‘climate-ready’ hybrids within the next five to 10 years.
“Growers will then be able to improve or sustain their yields and reduce risk through the selection of suitable hybrids,” he says.
This will be essential in the medium to long term, as the ‘risky heat window’ available to growers will become wider with increasing temperatures.
In the short-term, however, identifying and avoiding certain planting times will be a crucial management measure to reduce yield losses from extreme heat events.
“Currently, whenever sorghum growers get sufficient rain to plant, they have to make decisions about which hybrid they’re going to sow and when,” he says. “Such a decision influences the time of flowering and whether it will coincide with extreme temperatures.”
Using an existing farming systems model, modified for heat effects on sorghum, Professor Hammer and his team have shown that the most risky sowing time in warmer locations is during early to mid-October, before the high temperatures of late December and early January.
“Planting at this time increases the risk that high temperatures will coincide with the emergence and flowering of the seed head—a time when the crop is most susceptible,” Professor Hammer says.
Dr Scott Chapman, a senior researcher from CSIRO who presented the heat-tolerance research findings at the GRDC Updates earlier this year, says the key message to growers is that genetic variation for heat tolerance around flowering has been found. This is great news for the industry.
“We now know the trait characteristics that enable a sorghum plant to withstand extreme temperatures, and we have a screening procedure that allows us to identify better germplasm,” he says.
“With follow-on research it's entirely possible to develop improved heat-tolerant sorghum parent lines that can be fed into the commercial hybrid production system, to develop new hybrids within the next decade," Dr Chapman says.
Dr Scott Chapman discusses the benefits of heat tolerant sorghum in a GRDC video.
Prof. Graeme Hammer, QAAFI, The University of Queensland
07 3346 9463
Dr Scott Chapman, CSIRO Agriculture Flagship
07 3214 2254
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