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Resistance of Venturia inaequalis to multiple fungicides in Turkish apple orchards
Author(s) -
Polat Zühtü,
Bayraktar Harun
Publication year - 2021
Publication title -
journal of phytopathology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.53
H-Index - 60
eISSN - 1439-0434
pISSN - 0931-1785
DOI - 10.1111/jph.12990
Subject(s) - venturia inaequalis , myclobutanil , fungicide , apple scab , biology , horticulture , mycelium
Apple scab caused by Venturia inaequalis is one of the most economically important diseases of apple worldwide. Disease management is largely based on the frequent applications of fungicides, but fungicide resistance is a common problem. In this study, we monitored the development of resistance to four MBC, DMI and QoI group fungicides with different modes of action in V. inaequalis from apple orchards in Turkey. Sensitivity of V. inaequalis from 27 orchards in six provinces was evaluated to thiophanate‐methyl, myclobutanil, difenoconazole and kresoxim‐methyl by mycelium growth assay and molecular tools. Baseline sensitivity was determined in wild isolates of V. inaequalis from apple trees that had never been treated with any fungicides. EC50 value for thiophanate‐methyl, myclobutanil, difenoconazole and kresoxim‐methyl was 0.0992, 0.0315, 0.0048 and 0.0192 μg/ml, respectively. Of the 470 single spore isolates evaluated, 93.4% was very highly resistant to thiophanate‐methyl, while 27.5% and 50.2% were resistant and moderately resistant to myclobutanil, respectively. Difenoconazole and kresoxim‐methyl resistance were confirmed in 7.45 and 97% of the isolates tested, respectively. Molecular studies revealed that resistance to MBC fungicide, thiophanate‐methyl resulted from a mutation at codon 198 in β‐tubulin gene, while the G143A mutation of cytochrome b caused resistant to the QoI, kresoxim‐methyl. This study represents the first report of V. inaequalis resistance to several fungicides from apple orchards in Turkey. The resistance risk to these fungicides should be taken into consideration in the management of apple scab in Turkey.