Genomic Surveillance Identifies Global Strain of Emerging Wheat Disease Fungus

Study suggests that genomic surveillance may help track pathogen evolution and crop resistance to prevent crop failures

(April 11, 2023) - Pests and diseases may reduce global wheat yields by over 20%. A study published April 11 in the open access journal PLOS Biology by Sergio Latorre at University College London, U.K., and colleagues suggest that genomic surveillance may be an effective disease management tool with the ability to trace lineages of emerging crop diseases, and to identify genetic traits for breeding disease-resistant lines.

Wheat crops across the globe are threatened by wheat blast, an emerging fungal disease. However, disease-management strategies have been unsuccessful. In order to better understand emerging pathogen genotypes and lineages, researchers conducted both genome analyses and laboratory experiments. They genotyped and sequenced the genome of the pandemic wheat blast fungus and tested different lines of wheat for genetic resistance to blast fungus and susceptibility to fungicide.

The researchers found that the recent emergence of wheat blast in Asia and Africa was caused by a single clonal lineage of the wheat blast fungus and that outbreaks in Zambia and Bangladesh originated independently. They also show that breeds of wheat that carry the Rmg8 gene are resistant to this fungal strain, and that the fungus is sensitive to the fungicide strobilurin. These findings highlight how genomic surveillance may help plant breeders more effectively select traits to develop disease-resistant lines.

The research may provide new tools to help counteract emerging plant pathogens. However, future studies are needed to address the likelihood of crop diseases evolving resistance to pesticides and fungicides and to evaluate other potential strategies that reduce reliance on chemical inputs.

According to the authors, "The emergence of variants that are more damaging than the current genotypes is probable within short timescales. This could happen either through mutations or sexual recombination with endemic blast fungus populations. Such variants could have increased virulence and fungicide tolerance thus adding to the difficulty in managing the wheat blast disease. These findings underscore the need for genomic surveillance to improve tracking and monitoring of the wheat blast fungus on a global scale and identifying variants of concern as soon as they emerge."

Co-author Sophien Kamoun adds, "This project builds on the paradigm—best illustrated by the COVID-19 pandemic—that genomic surveillance adds a unique dimension to the coordinated response to infectious disease outbreaks. We need to remain vigilant and continue genomics surveillance of wheat blast in Africa and Asia to identify Variants of Concern (VOCs) as soon as they emerge."

Experts join forces to tackle spreading wheat disease

(April 11, 2023) - Genomic surveillance of plant pathogens is crucial in preventing global crop pandemics, particularly in the case of wheat, according to a recent study.

The study was conducted by an international team of researchers who collaborated across seven countries (United Kingdom, Japan, Bangladesh, Zambia, Mexico, Switzerland and the United States of America) to better understand wheat blast, a devastating fungal disease that has rapidly extended its range in recent years.

Wheat blast, Magnaporthe oryzae, has catastrophic effects on wheat crops. In 1985, it was first identified in Brazilian wheat fields and soon spread throughout the rest of the continent where it remained for three decades. However, in 2016, it emerged in Bangladesh and affected over 15,000 hectares of fields, leading to severe losses in wheat production up to 90%. Shortly after, Zambia also experienced a wheat blast pandemic, marking the first occurrence of the disease in Africa.

By sequencing and genotyping the pandemic lineage of wheat blast, the researchers found that outbreaks in Zambia and Bangladesh originated independently and were caused by the same clonal lineage of the wheat blast fungus. They also discovered that wheat varieties carrying the Rmg8 gene are resistant to the fungal strain and that the fungus is sensitive to the fungicide, strobilurin.

“Thanks to the prompt and public release of genomic data by the international scientific community through the OpenWheatBlast initiative, we were able to detect, track, and characterise the fungal lineage responsible for recent wheat blast outbreaks,” says Sergio Latorre, from University College London, one of the lead authors of the new study.

These findings demonstrate the potential of genomic surveillance to help plant breeders more effectively select traits to develop disease-resistant lines.

“The joint use of genomic surveillance and functional testing through laboratory experiments permit the establishment of genomics-informed integrated pest management practices and can guide plant breeders in the development of disease-resistant crops” says co-author Hernán Burbano, from University College London.

However, researchers caution that future studies are needed to address the likelihood of crop diseases evolving resistance to pesticides and fungicides, and to evaluate other potential strategies that reduce reliance on chemical inputs.

The authors suggest that “variants that are more damaging than the current genotypes” may emerge through mutations or sexual recombination with endemic blast fungus populations. These variants could have increased virulence and fungicide tolerance, adding to the difficulty in managing the wheat blast disease. Therefore, genomic surveillance is crucial to tracking and monitoring the wheat blast fungus on a global scale and identifying variants of concern as soon as they emerge.

Co-author Sophien Kamoun, from The Sainsbury Laboratory, adds, “This project builds on the paradigm—best illustrated by the COVID-19 pandemic—that genomic surveillance adds a unique dimension to the coordinated response to infectious disease outbreaks. We need to remain vigilant and continue genomics surveillance of wheat blast in Africa and Asia to identify Variants of Concern (VOCs) as soon as they emerge.”

Read full article in PLOS Biology

Citation: Latorre SM, Were VM, Foster AJ, Langner T, Malmgren A, Harant A, et al. (2023) Genomic surveillance uncovers a pandemic clonal lineage of the wheat blast fungus. PLoS Biol 21(4): e3002052. https://doi.org/10.1371/journal.pbio.3002052