Research by a Curtin University genomic scientist has identified a novel evolutionary process in the fungi that contribute to 10 to 40 per cent of crop losses worldwide.
These fungi, known as filamentous Ascomycetes, cause the diseases, wheat Stagonospora (Septoria) nodorum, tan (or yellow) spot, and canola blackleg, and contribute the most damage to Australian crops.
Led by biochemist and fungal pathology expert, Professor Richard Oliver, from Curtin’s Department of Environment and Agriculture, the research identified these fungi evolve faster and more dramatically than previously thought possible.
Professor Oliver said the research was conducted via a simple approach involving the comparison of genomes (all genes) of one species of fungus against others.
“We drew a chart known as a dot plot. Dot plots compare one genome on the x-axis with another on the y-axis; where DNA sequences are very similar, we place a dot,” Professor Oliver said.
“We would normally expect to see a diagonal line showing decay over evolutionary time. Instead, we saw dots in boxes.”
Professor Oliver said these results indicated a novel form of evolution, designated “mesosynteny”, that was not observed in any fungal, plant or animal groups.
“The mesosynteny mode of evolution, which is peculiar to this group of fungi, differentiates it from the more common micro and macrosynteny seen in other organisms,” he said.
“Mesosynteny appears to be restricted to filamentous Ascomycetes, which represent a group of fungi that include many important human, animal and plant pathogens.
“The phenomenon is most striking between species in the Dothideomycetes, a group which includes the most damaging pathogens on all major crops in Australia.”
Professor Oliver said the results demonstrated that the threat from rapidly evolving and mutating pathogens was ongoing.
“We normally think of these processes occurring on timescales measured in millions of years but we have clear evidence that new species of pathogens have evolved in the last 100 years,” he said.
“We can see that these pathogens overcome new resistance genes and fungicides in two to five years, and even see evolution occurring during the course of a growing season lasting only a few months.
“We need to ask how this happens and what evolutionary processes are allowing fungal pathogens to evolve so fast.
“It is tempting to speculate that mesosynteny allows these pathogens to acquire genes from other species, as we have seen in the case of tan spot, which we believe emerged as a disease only 70-80 years ago.”
Professor Oliver said the results should reinforce the need for vigilance in plant pathology at home and abroad.
“Our next step involves the sequencing of more species to include the pathogens that devastate the barley, pea, chickpea, lentil and faba bean crops,” he said.
“We want to see if mesosynteny has contributed to the pre-eminence of the Dothideomycetes fungal pathogens, and if can we find tools to enable breeders to select resistant crops.”
Professor Oliver’s research was funded by the Australian Grains Research and Development Corporation.
Professor Richard Oliver, Department of Environment and Agriculture, Curtin University
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Andrea Barnard, Public Relations, Curtin University
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