Canola has received an injection of new genetic diversity – including valuable stress-tolerance traits – due to a large-scale pre-breeding strategy that required the collaborative input of scientists in Australia, India and China.
The strategy involved drawing on canola progenitor (ancestral) species to resynthesise canola from scratch.
This time, however, canola was made using species that had not contributed previously to the cultivated canola gene pool. This resulted in a massive broadening of the genetic diversity available to breeding programs in the three partner countries.
Now, researchers based at the University of Western Australia and led by Dr Sheng Chen have announced the resynthesised canola has brought with it potentially valuable heat and drought-tolerance traits that can protect the flowering stage from these yield-damaging stresses.
If you were to see the plants, you would say they are mostly canola, but you can see some new characteristics, such as the leaf colour of the plants.
The new traits are undergoing detailed genomic analysis, even as the first generation of these new canola lines is being made available to canola breeders in Australia.
Dr Chen explains that the long-sighted project involved the partner countries playing to their strengths, with a special mention for Professor Surinder Banga of the Punjab Agricultural University, who played a prominent role carrying out the tricky, interspecies crosses.
Australia applied its formidable phenotypic screening capability, with researchers led by Professor Martin Barbetti targeting disease-resistance genes of interest to all three partner countries and Dr Chen focusing on heat and drought tolerance.
Dr Chen says it was exciting to see these new levels of tolerance appear once the widening of canola’s gene pool was achieved: “We were expecting some new tolerance to both biotic and abiotic stress because the genetic diversity of the resynthesised canola is much broader. So we were not surprised at the findings. But we are excited the traits we wanted came through and opened new possibilities.”
Of the material screened to date, Dr Chen has identified heat and drought-tolerance traits in three overall patterns:
- some lines are tolerant to drought only (these suffer yield losses in a heatwave);
- some lines have moderate levels of tolerance to both heat and drought, with no yield loss observed at field temperatures of 30°C to 32°C; and
- other lines expressed strong recovery after exposure to heat stress during a heatwave. Under these conditions, flowers turn white and become sterile, resulting in yield losses. The new material instead puts out side branches that produce pods that reverse the yield loss.
The findings are the result of five years of field trials that got underway in 2013 and terminated in 2017. That screening work identified a total of 14 lines with useful levels of stress tolerance.
More may exist, but it was not possible to screen all the germplasm generated by the partnership during the life of Dr Chen’s project. In addition, all the material was pre-tested to ensure that no traits were brought over from the wilder parental material that could negatively impact yields during a good season.
“If you were to see the plants, you would say they are mostly canola, but you can see some new characteristics, such as the leaf colour of the plants,” Dr Chen says.
Some lines exhibit a purple hue, due to some infusion of Brassica carinata (Abyssinian mustard). In other cases the pods are bigger than normally produced by canola because of genetic contributions from B. rapa (radish).
“You can see the infusion of diversity from the broader Brassica gene pool, but at the cytological level the chromosome arrangement has been verified as that of canola,” Dr Chen says.
The stress-tolerant material is now undergoing intensive genetic analysis. Dr Chen warns it is unlikely the newly identified tolerance traits will resolve down to variation at just one gene. More likely, it will involve complex interactions within a gene network.
While networks are tricky to place under selection during a breeding program, Dr Chen is hopeful a sufficient level of tolerance can be achieved based on the selection of just three or four genes. Functional markers then make it possible to carry the gene cluster through a marker-assisted breeding program.
He says GRDC investment played an integral role throughout the life of the project: “Broadening the genetic base of a cultivated crop is a foundational project and requires far-sighted and strategic investment decisions. Not all funding bodies have this capability and I personally want to thank GRDC for providing support that safeguards canola’s productivity into the future.”
- The project was headed by Professor Phil Salisbury of the University of Melbourne, starting in 2005.
- More information: Dr Sheng Chen, firstname.lastname@example.org
GRDC Research Code: UM00045, DAN00117, DAN00208