“Plants and their pathogens generally co-evolve over time. It’s similar to the way bacteria develop resistance to antibiotics. It’s like an arms race,” said Professor Robert Park, who was Dr Dinh’s PhD supervisor.
“In this case, even though the rust fungus had defeated the resistance gene, we wanted to understand how the gene worked, to see if it could be deployed with other genes, or even if its sequence could be altered to be made effective again.”
“Hoan undertook painstaking work over three years to isolate the gene from the barley genome, which is about the same size as the human genome. He found that the Rph3 gene is a new class of resistance gene in plants generally, which has led our research in a new direction that we think will advance rust resistance.”
The results were so remarkable that Dr Dinh initially worried he had made a mistake. “When I first found the gene, I was worried I had done something wrong because it was so unusual,” Dr Dinh said. “The majority of disease resistance genes belong to a different gene family. It felt great to be vindicated.”
The use of resistance genes in crop species such as wheat and barley has long been considered the most cost-effective and environmentally friendly method of preventing rust outbreaks. These pathogens spread over thousands of kilometres and have caused huge epidemics that have resulted in hundreds of millions of dollars in damage. While they continue to have an impact on production, it has been estimated that genetic resistance saves Australian wheat and barley growers more than $1 billion every year.
Professor Park, a global leader in rust research from the University of Sydney’s Plant Breeding Institute, says that to date, 28 rust-resistance genes in barley have been identified worldwide. Only four of these have been isolated so far, three by the Plant Breeding Institute (Rph3 being the third).