An international research collaboration has for the first time isolated not one but two stem rust resistance genes, in a major breakthrough in the global effort to control this devastating crop disease.
The two genes – sourced from bread wheat’s wild progenitor (ancestor) species – provide new insights into the basis of resistance while also delivering useable agronomic advances.
One of the genes – isolated by the Australian team – has been found to confer resistance to all known stem rust races. It can also work synergistically with other genes in ways that further strengthen the plant’s base resistance levels.
The pioneering gene discoveries, which are the culmination of four to five years of research, have been hailed around the world as a food security boon since both genes are underexploited in cultivated wheat varieties.
Further, both genes are effective against the Ug99 stem rust races that have been threatening 90 per cent of the world’s wheat varieties and, as such, 20 per cent of the world’s caloric intake.
The two genes are a game-changer for pre-breeders on many levels. Looking to the future, they also provide a stepping stone to develop new breeding technologies in which combinations of genes are used to build durable, broad-spectrum and robust forms of disease resistance.
Two teams worked independently to each isolate one gene. The Sr33 gene was isolated in Australia in a GRDC-supported program, and the Sr35 gene was isolated in the US. Both teams deliberately targeted agronomically important forms of resistance for the gene discovery projects.
A spirit of collaboration prevailed between the two teams, which shared information, materials and resources.
That collaborative approach proved vital, says Dr Evans Lagudah, chief research scientist at CSIRO Plant Industry, who led the Australian team. “It is opening up new molecular breeding approaches for wheat improvement,” he says
“This includes the means to insert both genes into a common location in the wheat genome and thereby simplify breeding because adjacent genes tend to be inherited together.
“This could prove important, since no stem rust race is virulent on plants containing both Sr33 and Sr35 because collectively these two genes provide resistance to all known stem rust races when co-deployed,” Dr Lagudah says.
To reach this milestone, both the Australian and US research teams worked within the Borlaug Global Rust Initiative, which provided open communication channels among global researchers and funds from the Bill and Melinda Gates Foundation.
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