Rust Resistance Gene Stewardship and Durable Cereal Rust Resistance, an Australian Perspective

Jeff Ellis¹, Evans Lagudah¹, Sam Periyannan¹ Rohit Mago¹, Linda Tabe¹, Ian Dundas², Wolfgang Spielmeyer¹, Michael Ayliffe¹ and Peter Dodds¹

From having been a ‘hot spot’ for stem rust up to the 1970s, Australia has remained free of epidemics of this disease since. This has been due mostly to the use of multiple resistant varieties each possessing more than one and diverse resistance genes in a location where sexual reproduction of Puccinia graminis tritici (Pgt) does not occur. The effect of growing resistant varieties has greatly reduced in season Pgt spore inoculum, which in turn reduces the number of virulent mutants arising that overcome resistance.  Similar success in controlling the stripe rust pathogen Puccinia striiformis tritici (Pst) has not yet been achieved. We are attempting to increase levels and durability of resistance through the development of DNA markers, applicable across broad sources of germplasm, for important rust resistance genes in hexaploid wheat. New sources of resistance have also been developed by ‘domesticating’ alien resistance genes from related species by chromosome engineering. In addition, we have cloned two multi-pathogen resistance genes that confer durable, partial resistance to stem rust, and two gene-for-gene type stem rust resistance genes. With these and other resources, we are developing strategies for deploying cassettes of resistance genes in GM wheat.