Wheat disease threatening global yields

The spread of wheat pests and diseases may reduce global wheat yields by over 20%. A study, published in open access journal PLOS Biology by Sergio Latorre at University College London, has suggested that genomic surveillance may be an effective disease management tool due to its ability to trace lineages of emerging crop diseases and identify genetic traits for breeding disease-resistant lines.

Wheat blast, Magnaporthe oryzae, is an emerging fungal disease threatening wheat crops across the globe, with management strategies unsuccessful. To better understand the disease, 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.

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

The research may provide tools to help counteract emerging plant pathogens, but further study is needed to address the likelihood of diseases evolving resistance to pesticides and fungicides, as well as to evaluate potential strategies that reduce reliance on chemicals.

The authors of the study said, “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.”

Sophien Kamoun, co-author, said, “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.”

Image caption: A wheat field in the Mpika District, Muchinga Province, Zambia, showing symptoms of wheat blast during the outbreak of March 2018. Image courtesy of Batiseba Tembo, Zambia Agriculture Research Institute, under CC-BY 4.0