Miller Magazine Issue: 141 September 2021

40 MILLER / september 2021 NEWS A team of scientists have identified a promising resistance gene that could help fight a devastating fun- gus called stem rust, which attacks wheat crops and threatens global food security. Stem rust, a virulent wheat disease caused by the fungus Puccinia graminis, has become a major threat to wheat crops in Africa and oth- er regions. Breeders and farmers need access to more resistant germplasm (seeds) to protect wheat yields from losses due to disease epi- demics, like the Ug99 strain which is attacking wheat crops in Africa and the Middle East. Now a team of Australian and US American researchers have identified a resistance gene to fight stem rust. The discovery, published in Nature Plants in late July, also identifies a gene in the fungus that triggers this resistance in the host plant, and together these findings pro- vide a pathway to help wheat growers defend against this disease. Wheat provides roughly 20 per cent of calo- ries and protein for human nutrition worldwide. Stem rust is among the world’s most devastat- ing plant diseases, and can completely destroy a crop of wheat in a matter of weeks. Dr Peter Dodds, Chief Research Scientist at Australia’s national science agency CSIRO, said this was yet another weapon in the armory to stay one step ahead of wheat stem rust glob- ally. “Discovery of this resistance gene contin- ues our effective collaboration with internation- al partners that has already resulted in great advances to build resistance to this potentially devastating pathogen,” Dodds stressed. This new research will help researchers and wheat breeders to introduce multiple resistance genes into a wheat variety to build durable re- sistance to wheat rusts. This novel approach to providing durable resistance has been pio- neered by CSIRO and the U.S.-based non-profit 2Blades Foundation, and is bolstered through a recent demonstration of a “gene stack” of five cloned Sr genes for effective stem rust resis- tance in wheat. The resulting new wheat variety shows exceptional resistance to stem rust. Introducing a multi-gene stack is much more precise and quicker than conventional breed- ing, which can take decades to produce a wheat variety resistant to wheat rust diseas- es. This new method will also ensure that the desirable trait (determined by multiple genes) will not segregate and be lost in subsequent breeding. The most effective and environmentally sound way to defend against wheat rust dis- eases is through the deployment of such resis- tance genes in wheat varieties. This is particu- larly important in developing countries, where the fungicides used to combat rust disease may be expensive or unavailable. New research helps combat devastating disease of wheat plants Dr. Peter Dodds Chief Research Scientist CSIRO