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Azole fungicide sensitivity and molecular mechanisms of reduced sensitivity in Irish Pyrenopeziza brassicae populations
Author(s) -
Bucur Diana E.,
Huang YongJu,
Fitt Bruce D. L.,
Kildea Steven
Publication year - 2024
Publication title -
pest management science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.296
H-Index - 125
eISSN - 1526-4998
pISSN - 1526-498X
DOI - 10.1002/ps.7219
Subject(s) - fungicide , tebuconazole , biology , azole , horticulture , agronomy , antifungal , microbiology and biotechnology
BACKGROUND Light leaf spot, caused by Pyrenopeziza brassicae , is amongst the most damaging diseases of winter oilseed rape ( Brassica napus ), and currently the sterol 14α‐demethylase (CYP51) inhibitors (azoles) represent the main class of fungicides used to control light leaf spot development. However, a shift in sensitivity to azole fungicides in P. brassicae populations has been observed in different European countries, including Ireland. RESULTS To assess the sensitivity status of Irish P. brassicae populations to azole fungicides, three collections of P. brassicae from 2018–2020 were tested in vitro against tebuconazole and prothioconazole‐desthio, and the PbCYP51 gene targeted by this class of fungicides was genotyped in different isolates. A change in sensitivity to azole fungicides was observed and differences in sensitivity to tebuconazole between Irish populations were present. There were two substitutions within PbCYP51 (G460S and S508T) and inserts of different sizes in its promoter region. The presence of the G460S/S508T double mutant was reported for the first time, and the diversity in insert size was greater than previously known. Compared to wild type isolates, those carrying G460S or S508T were less sensitive to both fungicides and, where inserts were also identified, they further reduced sensitivity to azole fungicides. CONCLUSIONS The results of this study suggest that azole fungicides are still very effective in controlling light leaf spot in Ireland. However, using azole fungicides in mixtures of fungicides with different modes of action is recommended. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.