Trait find may lead to climate-proof wheat

A common (genetic) denominator has been discovered for wheat’s acute sensitivity to stress – from drought, heat or frost – at flowering. It opens the way for researchers to develop a single trait that can stabilise yields in even the most challenging seasons.

The finding stems from the discovery of a common biological response to different kinds of environmental stresses. This points to the existence of a single genetic trait able to protect cultivars from multiple stresses.

Also, perhaps for the first time, this highly complex field of research is revealing that out of the phenomenal knowledge expansion of the past few years there may emerge a comparatively simple tool for plant breeders – a single set of molecular markers that will allow the development of the most climatically robust varieties yet grown.

This research into the existence of a single trait has already reached the point where genetic mapping – from which molecular markers are developed – has reached an advanced stage.

The ‘single-trait’ approach was the brainchild of Dr Rudy Dolferus of CSIRO Plant Industry in Canberra. Dr Dolferus arrived at this concept by integrating many, disparate field observations in which plants subjected to different stresses all ultimately responded the same way – by aborting the development of pollen.

Dr Dolferus is funded by the GRDC and collaborates with frost-tolerance researcher Dr Ben Biddulph, from the Department of Agriculture and Food, Western Australia.

At the heart of the finding is this issue of pollen sterility. “It looks like all kinds of variation in the environment can cause pollen sterility and that made me think: there can’t be a thousand ways to induce pollen sterility in the plant, the plant must have a common control pathway,” Dr Dolferus explains. “Otherwise the sheer dimensions and biochemistry of the plant would be ridiculously complex.”

Ground Cover has reported on the particular sensitivity of pollen formation to stress (issue 82, September–October 2009) but more recently Dr Dolferus has identified the genetic variance within this common control pathway that results in pollen being either extremely sensitive or highly tolerant to different environmental stresses.

This is the key to being able to genetically map a stand-alone trait for multiple stress resistance. Dr Dolferus has made considerable progress with this.

“I started working to improve tolerance to drought stress in 2007, but found the mechanism to be equally relevant to other stresses including heat, cold and frost,” Dr Dolferus says.

“And all these different stresses converge on the same biological control pathway and the plant’s ‘decision’ to go ahead or to abort pollen development.”

Single trait find

Dr Dolferus’s discovery is shaping up to be the next ‘step change’ in the capacity of plant breeders to protect wheat’s yield potential and yield resilience in the face of climate variability. Normally, researchers work on each of the different stresses separately, using different germplasm and producing a multitude of weakly associated, genetically linked traits with little overlap among different laboratories.

“What we did was keep the germplasm the same and look at the biological impact on pollen fertility of different types of stress,” Dr Dolferus says. The outcome is the discovery that no matter which stress, the biochemical signals ultimately funnel to a common molecular switch. Researchers can now identify germplasm with tolerance to one stress that carries over to other stresses.

When it comes to frost, Dr Dolferus is also breaking the stress down to component parts – such as drops in temperature and the resulting increase in humidity in the canopy or the increase in far-red light that occurs at sunset – and looking at their impact on pollen as separate tolerance events.

“Our hypothesis is that plants that are better prepared in the lead-up to frost are better able to maintain pollen fertility when frost hits,” he says.

“It is like a gigantic jigsaw puzzle. But the thing is, when you look at the different stresses and you look for the overlap, you might be able to identify these control pathways better. This is a long-term process but this is the best tool we have, to date, to understand the problem.”
 

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