Origin of deadly wheat pathogen discovered by academic partnership

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The origin of a deadly wheat pathogen which threatens a vital global food source has been identified by an international team of academic researchers including two professors from the University of the Free State in South Africa.

First identified in Africa two decades ago, the strain of the stem rust fungus, ‘Ug99,’ was said to threaten the global wheat supply due to its ability to attack most varieties planted across the world. Rust diseases cause substantial crop losses each year. It was first detected in Uganda in 1998 and described in 1999 and has since given rise to an asexual lineage that has spread through Africa to the Middle East causing devastating damage to wheat crops.

Professor Zakkie Pretorius and Professor Botma Visser, researchers from the Department of Plant Sciences, University of the Free State in South Africa, joined forces with the University of Minnesota; the Commonwealth Scientific and Industrial Research Organization (CSIRO); and Australian National University, to uncover the basis of the stem rust fungus strain Ug99’s virulence by examining the pathogen’s genome.

They determined that the pathogen can be traced to a rarely observed phenomenon where two different rust strains fuse together and exchange intact nuclei. This is said to create a hybrid strain with a wider host range than its original parents.

“Ug99 is an imminent threat to global food security due to its wide virulence and potential ability to spread across continents and oceans to infect distant wheat crops,” said Professor Zakkie Pretorius of the University of the Free State.

Dr Melania Figueroa, from the Commonwealth Scientific and Industrial Research Organisation (CSIRO), Australia, adds: “This information will be critical for deciphering the genetic basis and evolution of rust virulence on wheat and for monitoring the global movements of the pathogen.”

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