Phytotron plant growth chambers at Charles Sturt University, Wagga Wagga, will play a starring role in new research aimed at identifying genes that might make wheat plants less vulnerable to late frost.

Titled ‘Developing new genetic approaches to decreasing the reproductive frost sensitivity of wheat’, the project is one of three GRDC investments – collectively valued at $10 million – researching methods of reducing the impact of spring frosts on wheat yields.

CSIRO senior principal research scientist Dr Chris Helliwell, who is leading the project, says it will build on successful research in crops such as wheat, barley and canola to identify and better understand the genes that control the different stages of growth.

The university’s Phytotron has multiple growth chambers that can be temperature, light and humidity controlled, including three that are specially equipped for simulating frost conditions.

Gene mapping

The five-year project involves gene mapping to identify genes or genetic regions associated with decreased frost sensitivity in a panel of about 400 wheat varieties subjected to the same stress.

The wheat varieties that will be gene mapped include a combination of some varieties that are available now, Dr Helliwell says.

“We have also got a collection of historic varieties that represent the Australian breeding pool for wheat, so that gives us more genetic diversity to look at.”

Researchers will also attempt to modify genes that might provide improved tolerance for evaluation later in the project.

Based on protocols developed by former CSIRO plant geneticist Dr Rudy Dolferus, plants will first be grown in a standard chamber under ‘normal’ day and night temperatures, then moved into a frost chamber once they reach their most-sensitive stage.

CSIRO senior principal research scientist Dr Chris Helliwell. Photo: courtesy Chris Helliwell

We’re targeting an early stage in reproductive development – young microspore – where the cells that are going to become the pollen are dividing and segregating the genetic information to the individual pollen grains, Dr Helliwell says.

“That stage is particularly sensitive to frost. So we grow the plants until they get to that stage, transfer them into a cabinet that’s running with a normal day of about 21°C and a cold night of minus 3°C for about eight hours, leave them there for four days and move them back to normal conditions.”

Researchers will then grow the plants to maturity, and score each for how much damage it suffered by counting how many fertile grains were made.

Dr Helliwell says the simulation is less complex than what happens in the field, but the protocol was able to distinguish between the cold-tolerant variety Young and the cold-sensitive variety Wyalkatchem.

“That protocol can reproduce the frost rankings the National Frost Initiative developed for other varieties as well, so we think it’s a reasonably good way to reproducibly assess frost tolerance,” he says.

“But we also acknowledge that it’s not necessarily the same as a frost in the field, because every frost in the field is going to be different.”

Improved tolerance

He says controlled-environment experiments take time and it will likely be at least three years before the researchers understand the genetics and can identify markers for genes that control frost tolerance.

“Because it’s difficult for plant breeders to select for frost tolerance, current varieties may or may not have those particular markers,” he says.

“Once you know what they are, breeders can then select for the lines that have those markers in them as part of their breeding process. There’s always a trade-off between entering the flowering phase early, so you’ve got a good grain set before you get into the really hot weather of summer, and avoiding unpredictable late frosts.

“For every location there’s a window that you want to try and land in. What we’re aiming to do in this project is to improve the tolerance by 1°C – by having something that survives better at a 1°C lower temperature – helping to extend that window.”

Spring frost damage has been estimated to cost Australian wheat growers $360 million a year by reducing grain number and weight, increasing screenings.

More information: Chris Helliwell, chris.helliwell@csiro.au