April 12, 2021
Genomic tools will inform pathogen evolution
Vancouver, BC — Disease causing fungal pathogens jeopardize global food production by reducing crop yield and quality. Stripe rust, caused by the fungus Puccinia striiformis, is one of the most devastating pathogens of wheat and barley in Canada, including BC’s Peace Region.
Over the last decade large areas of North America, notably in Western Canada, have seen a major change in the stripe rust fungus population. Novel strains that are more virulent to previously resistant, important wheat cultivars have become more prevalent. This means a possible introduction of novel strains, or that fungal strains are mutating. Traditionally, mutations in DNA (genes) play an important role in creating genetic diversity which allows the pathogen strains to adapt to changing environments and overcome adversity. In this case, however, defeating disease resistance in the elite wheat cultivars means less crop production.
In many organisms, shuffling genetic information in the population often occurs through recombination of sex chromosomes and the transmission of pieces of genetic material to the progeny. With limited possibility for sexual reproduction, as for the stripe rust fungus in North America, an alternative process can occur where whole nuclei are exchanged in a unique, complex process called the hybridization of somatic cells; there is a genetic exchange without sex, and cells simply fuse. This can occur when two different strains grow their mycelium in the same wheat plant. Determining the frequency of such events is important for rust disease management in wheat crops and for food security.
With funding from Genome BC, Dr. Gurcharn Singh Brar with the University of British Columbia (UBC) and Dr. Guus Bakkeren with Agriculture and Agri-Food Canada are studying single cells to identify the prevalence of this adaptive somatic hybridization mechanism and how it may contribute to genetic variation of rust fungi in the population. This unique approach will help to lay a foundation for the use of rapid, single-cell genomics-based tools for ongoing surveys of cereal rust pathogens.
“Stripe rust is an emerging disease issue for Canada and most of the existing strains of the causal pathogen are better adapted to warmer climates. To develop wheat varieties with durable resistance, we must understand both the pathogens and their hosts,” says Dr. Brar, an Assistant Professor in Plant Science at UBC. “On the one hand, geneticists and breeders are focusing on strengthening the immune system of wheat, but on the other hand, these pathogens evolve within short periods of time to defeat such plant immunity. Through our research we are trying to understand the biological forces which result in the changes in these pathogens.”
Pathogen evolutionary change is fundamental to our understanding of controlling infectious diseases that affect economically important crops. Using the latest advances in genomics this study focuses on dissecting the mechanisms which pathogens use to evolve and overcome host resistance. Cutting-edge sequencing platforms provide whole genome sequencing of the pathogens and will allow the team to precisely study the content of each nucleus in rust spores and trace the genetic make-up of the pathogen strains. This work will also inform and complement ongoing Canadian-led genomics research in wheat with respect to breeding for resistance against these diseases.
“Our investment will provide a foundational understanding of the progression of pathogens attacking Canadian crops,” says Dr. Federica Di Palma, Vice President, Sectors and Chief Scientific Officer at Genome BC. “Food security is an essential component of our health and well-being – this is one step towards a better understanding of crop fungal pathogens.”
This work was funded through Genome BC’s Sector Innovation Program which seeks to support projects that will address the needs of each key sector and have the potential to generate social, environmental and economic benefits for British Columbia in the future.
Contact: Jennifer Boon, Communications Manager, Public and Media Relations