A February meeting of many of the world's leading barley rust geneticists in Sydney led to discussions on a wide range of issues.

These included:

• wild relatives of barley as a source of new rust resistance;
• the latest in developing DNA markers to improve the efficiency of selecting for important rust resistance genes in breeding;
• the isolation and characterisation of rust resistance genes from barley;
• non-host resistance; and
• new approaches to accelerate gene discovery, characterisation and deployment into agriculture.

The two-day meeting was held at the University of Sydney's Plant Breeding Institute (PBI).

About 20 scientists gathered, including Australian researchers from CSIRO and the University of Sydney, along with researchers from the Netherlands (Wageningen Agricultural University), Saudi Arabia (King Abdullah University of Science and Technology), the United Kingdom (the Sainsbury Laboratory), New Zealand (the New Zealand Institute for Plant & Food Research Limited) and Germany (JKI).

Australian researchers provided an update on GRDC-invested research on leaf rust in which efforts have targeted identifying new resistance and isolating several important rust resistance genes.

Leaf rust focus

This research has focused on leaf rust, caused by Puccinia hordei, which is the most common and damaging rust disease on barley worldwide and was estimated in 2009 to cause some $21 million in annual losses on average in Australia.

Reports were made about the isolation of three leaf rust resistance genes, and developing high-throughput markers for six important resistances that include the three durable adult plant resistance (APR) genes (Rph20, Rph23 and Rph24).

Importantly, the markers have allowed us to confirm the presence of these genes in Australian barley cultivars (for example, Flagship and Barque carry Rph20, while Oxford and Starmalt carry both Rph20 and Rph24).

These markers have also greatly enhanced efforts to postulate the presence of uncharacterised sources of APR to leaf by focusing efforts on lines that lack the three genes and yet carry APR.

The species Hordeum bulbosum and Hordeum spontaneum have proven to be rich sources of new genes conferring resistance to various barley diseases, including leaf rust.

Dr Paul Johnson from New Zealand has been heavily engaged in work that has led to the introduction new leaf rust resistance from H. bulbosum.

Work has been underway at the PBI for some time to introduce some of these resistances into locally adapted barley for use by our breeders.

At least four characterised leaf rust resistance genes originate from H. spontaneum, and work is being conducted in Germany and at PBI to characterise several new sources of resistance from this species.

Genetic basis of resistance

Dr Rients Niks from the Netherlands has spent an entire career investigating the genetic basis of partial resistance to P. hordei and why plants are resistant to most pathogens - for example, why is barley not infected by the wheat leaf rust pathogen Puccinia triticina?

His research has revealed some similarities between resistance to adapted pathogens such as P. hordei and other non-adapted pathogens such as P. triticina.

Professor Krattinger and Dr Yajun Wang from Saudi Arabia, and Dr Matt Moscou from the UK, also outlined their research in this area.

Their research highlighted the increasing utility of sequencing the genomes of barley cultivars known to carry rust resistance and the development of a pan-genome to provide more cultivar specific sequence information.

This approach greatly enhances rust resistance research as it reduces the reliance on the reference genome derived from the leaf rust susceptible cultivar Morex, which more often than not does not carry the resistance allele of interest.

Progress in this area of research has accelerated in recent times with the advent of powerful and more-affordable genome sequencing - for example Professor Krattinger's group recently sequenced a barley cultivar for about US$30,000 - which would have been unheard of only a few years ago.

The meeting provided a perfect opportunity for PhD students Hoan Dinh, Rouja Haghdoust, Mehnaz Mehnaz and Xiaohui Yu to showcase their research on barley rust genetics and network with international scientists.

GRDC Research Codes: 9175448, 9175952, 9176057