BREEDING FOR resistance in Australian cereals has been very successful in controlling rust diseases, but there is still room for improvement as evidenced by recent losses to leaf rust in eastern Australia and to stem rust in the west. CSIRO Plant Industry, with GRDC support, is working on several biotechnology approaches that are aimed at strengthening the ability to produce durable resistance to rust diseases.
The first approach is to provide simple and efficient breeding tools that will enable durable stem rust resistance genes to be combined or "pyramided" in new wheat varieties. The tools, called DNA markers, can allow wheat breeders to rapidly and accurately determine whether or not good genes are present in their breeding lines. The CSIRO team are targeting several wheat stem rust-resistance genes. This includes two highly effective genes, which were introduced into wheat from rye by traditional breeding many years ago but are not used in bread wheat in Australia because of an associated genetic defect that causes "sticky dough". Other groups are attempting to separate resistance and sticky dough by conventional breeding, and the DNA markers identified at CSIRO will assist in breeding bread wheat with the new improved versions of these genes.
A second biotechnology approach involves isolating rust-resistance genes by DNA cloning. Although this work is still at an experimental stage, it will provide a powerful rust-resistance breeding approach in the future. The CSIRO group was the first in the world to clone a rust-resistance gene, when they succeeded in cloning the L6 rust-resistance gene from flax. The information about rust-resistance genes in flax has been essential in designing experimental approaches to clone rustresistance genes from wheat. Based on the premise that it is always good to know as much as possible about the enemy, they have also focused some research on the rust fungus itself, again using the flax rust model. In another world-first, they recently isolated a gene from flax rust, called an "avirulence gene". Rust strains that carry this gene turn on L6 rust resistance. This means that the two genetic components of the molecular switch for rust resistance have now been isolated. The team is now carrying out some exciting experiments aimed at completely novel forms of rust resistance, based on their knowledge of the flax rust-resistance switch. The goal is to bring together the proven traditional forms of rust control with the newer biotechnology approaches, and thereby provide more effective and long-lasting forms of cereal rust resistance.
Program 3 Contact: Dr Jeff Ellis 02 6246 5421 email Jeff.Ellis@csiro.au