The project successfully delivered a new and robust molecular marker capable of identifying the smallest chromosomal introgressed segment containing the stem rust resistance gene, Sr22. This gene currently provides resistance to all stem rust isolates in Australia, India and against Ug99 and its derivatives. Furthermore tests conducted in Ethiopia, by CIMMYT scientists, where other virulent stem rust races adapted to durum wheats occur, showed that Sr22 was effective against the specialised Ethiopian races.
The use of the robust Sr22 molecular marker as breeding tool will be deployed in India through the ACIAR-funded project CIM/2005/020, 'Molecular marker technologies for faster wheat breeding' and in Australia through the Australian Cereal Rust Control Program's relationships with breeding companies.
The research team recommended that researchers in project CIM/2005/020 make every effort in the use of the Sr22 breeding tool to combine with other effective resistance genes in their germplasm development rather than Sr22 alone. As well, wheat breeders must consider whether to restrict the use of Sr22 to bread wheats and avoid durum wheats, in order to extend the lifespan of Sr22 resistance.
In addition the SRA project was able to show that adult-plant stem rust resistance genes were present in the targeted Australian varieties, such as Hartog, as well as the North American variety Thatcher (known for its specific interaction with a broad-spectrum adult plant resistance gene, Lr34/Yr18). In order to progress with marker development for the Thatcher-based adult plant resistance genes, a new set of genetic populations will be required due to the confounding rust-resistance phenotypes observed with the Australian cultivars Meering and Oxley.
This Small Research Activity (SRA) enabled interaction with Indian Council of Agricultural Research partners and field-rust evaluations at different sites in India. The team concluded that the location at the Indian Agricultural Research Institute regional station, Wellington, provided one of the consistent sites for achieving rust epidemics for experimental studies. Visits to Australia by Drs Vinod Prabhu (IARI, Delhi) and Mohinder Prashar (DWR, Shimla) aided the development of the new project CIM/2007/084 to follow up on the findings of the SRA. The project aims to develop molecular markers to broaden the genetic base for stem rust resistance genes effective against Ug99.