Wheat is Australia’s primary agricultural food crop and a globally important food crop which is constantly under threat due to the emergence of new fungal pathogen strains. For example, the stem rust strain Ug99 which first appeared in the Eastern parts of Africa has the potential to damage more than 60% of the wheat cultivars grown worldwide. As part of a global initiative (Durable Rust Resistance in Wheat) to counter the spread of Ug99, wheat rust research at CSIRO is focused on molecular genetic characterisation of stem rust resistance genes from wild relatives of wheat, which are effective against Ug99 and other virulent wheat stem rust strains.
Using induced mutations and arduous positional cloning, we were successful in isolating one of the first stem rust resistance genes from wheat, Sr33, which has also proven to be effective against Ug99. With the knowledge of Sr33 and advancements in sequencing technologies, a rapid resistance gene cloning technique called Mutagenesis, Resistance gene enrichment and Sequencing (MutRenSeq) was developed in partnership with the John Innes Centre, UK. MutRenSeq has enabled cloning of two additional stem rust resistance genes, namely Sr22 and Sr45, which are also effective against Ug99 and other virulent stem rust strains. This success has paved the way for the rapid isolation of new rust resistance genes, enabling the possibility of multiple transgene cassette deployment for durable management of rust diseases in wheat. In addition to the identification of rust resistance genes in wheat, the technology is currently being utilised for rapid identification of disease resistance genes in other agriculturally important crops such as barley, potato, soybean and rye.