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Monitoring of Brazilian wheat blast field populations reveals resistance to QoI,DMI, and SDHI fungicides |
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| Authors: | Samara N C Vicentini Priscila S Casado Giselle de Carvalho Silvino I Moreira Adriano F Dorigan Tatiane C Silva Abimael G Silva Adriano A P Custódio Ana Carolina S Gomes João L Nunes Maciel Nichola Hawkins Bruce A McDonald Bart A Fraaije Paulo C Ceresini |
| Institution: | 1. Department of Crop Protection, Agricultural Engineering, and Soil (Departamento de Fitossanidade, Engenharia Rural e Solos), UNESP - São Paulo State University, Ilha Solteira, São Paulo, Brazil;2. Department of Crop Protection, Agricultural Engineering, and Soil (Departamento de Fitossanidade, Engenharia Rural e Solos), UNESP - São Paulo State University, Ilha Solteira, São Paulo, Brazil
Vale do Paraná S.A. Álcool e Açúcar, Suzanápolis, São Paulo, Brazil;3. Department of Plant Pathology, UFLA - Federal University of Lavras, Lavras, Minas Gerais, Brazil;4. Paraná Rural Development Institute, IDR - Paraná/IAPAR, Londrina, Paraná, Brazil;5. Brazilian Agriculture Research Corporation - EMBRAPA Wheat, Passo Fundo, Rio Grande do Sul, Brazil;6. Biointeractions and Crop Protection, Rothamsted Research, Harpenden, UK;7. Plant Pathology Group, Institute of Integrative Biology, ETH Zürich, Zürich, Switzerland |
| Abstract: | Wheat blast is one of the most important and devastating fungal diseases of wheat in South America, South-east Asia, and now in southern Africa. The disease can reduce grain yield by up to 70% and is best controlled using integrated disease management strategies. The difficulty in disease management is compounded by the lack of durable host resistance and the ineffectiveness of fungicide sprays. New succinate dehydrogenase inhibitor (SDHI) fungicides were recently introduced for the management of wheat diseases. Brazilian field populations of the wheat blast pathogen Pyricularia oryzae Triticum lineage (PoTl) sampled from different geographical regions in 2012 and 2018 were shown to be resistant to both QoI (strobilurin) and DMI (azole) fungicides. The main objective of the current study was to determine the SDHI baseline sensitivity in these populations. Moderate levels of SDHI resistance were detected in five out of the six field populations sampled in 2012 and in most of the strains isolated in 2018. No association was found between target site mutations in the sdhB, sdhC, and sdhD genes and the levels of SDHI resistance, indicating that a pre-existing resistance mechanism not associated with target site mutations is probably present in Brazilian wheat blast populations. |
| Keywords: | fluxapyroxad fungicide resistance nontarget site resistance Pyricularia oryzae Triticum lineage second-generation carboxamides succinate dehydrogenase inhibitors |