High frequency of fungicide resistance‐associated mutations in the wheat yellow rust pathogen Puccinia striiformis f. sp. tritici

• Published in: Pest management science Vol. 77; no. 7; pp. 3358 - 3371
• Main Authors: Cook, Nicola M, Chng, Soonie, Woodman, Tamsin L, Warren, Rachael, Oliver, Richard P, Saunders, Diane GO
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 01-07-2021; Wiley Subscription Services, Inc
• Subjects: Cereals; Cyp51; CYP51 gene; demethylation inhibitor; Evolution; fungicide resistance; Fungicides; Homology; Inhibitors; Mutation; Pathogens; Pest control; Pest resistance; Pesticides; plant pathology; Puccinia graminis; Puccinia striiformis; Puccinia striiformis f. sp. tritici; Rust fungi; SDHI; Soybeans; Stripe rust; Substitutes; Succinate dehydrogenase; triazole; Wheat; New Zealand; China; SDHI; fungicide resistance; Puccinia striiformis f. sp. tritici; Cyp51; demethylation inhibitor; plant pathology; triazole
• ISSN: 1526-498X; 1526-4998
• DOI: 10.1002/ps.6380

BACKGROUND
Reliance on fungicides to manage disease creates selection pressure for the evolution of resistance in fungal and oomycete pathogens. Rust fungi (Pucciniales) are major pathogens of cereals and other crops and have been classified as low‐risk for developing resistance to fungicides; no case of field failure of fungicides in a cereal rust disease has yet been recorded. Recently, the Asian soybean rust pathogen, Phakopsora pachyrhizi evolved resistance to several fungicide classes, prompting us to screen a large sample of the globally widespread wheat yellow rust pathogen, Puccinia striiformis f. sp. tritici (Pst), for mutations associated with fungicide resistance.
RESULTS
We evaluated 363 Pst isolates from Europe, the USA, Ethiopia, Chile, China and New Zealand for mutations in the target genes of demethylase inhibitor (DMI; Cyp51) and succinate dehydrogenase inhibitor (SDHI; SdhB, SdhC and SdhD) fungicides. A high proportion of Pst isolates carrying a Y134F DMI resistance‐associated substitution in the Cyp51 gene was found among those from China and New Zealand. A set of geographically diverse Pst isolates was also found to display a substitution in SdhC (I85V) that is homologous to that reported recently in P. pachyrhizi and linked to SDHI resistance.
CONCLUSION
The identification of resistance‐associated alleles confirms that cereal rusts are not immune to fungicide resistance and that selection for resistance evolution is operating at high levels in certain locations. It highlights the need to adopt fungicide resistance management practices and to monitor cereal rust species for development of resistance. © 2021 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.
Analyses of 363 wheat yellow rust isolates from Europe, the USA, Ethiopia, Chile, China and New Zealand identified mutations in target genes of demethylase inhibitor and succinate dehydrogenase inhibitor fungicides.
© 2021 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.