Resistance Evaluation Following Successive Passages on Thiophanate-Methyl Against Alternaria alternata
DOI:
https://doi.org/10.48165/jpds.2026.21.01.15Keywords:
Grape, Vitis vinifera, Botrytis cinerea, grey mould, thiophanate-methyl, fungicide resistance, successive passages, resistance managementAbstract
Grey mould of grape (Vitis vinifera L.), caused by Botrytis cinerea Pers. ex Fr., is one of the most serious post-harvest diseases worldwide, causing 10–50% losses in grape production and storage. Effective management of the pathogen is essential for maintaining fruit quality, and systemic fungicides are widely used for its control. However, the continuous use of fungicides has resulted in the development of fungicide resistance in B. cinerea, reducing the effectiveness of chemical disease management.
The present investigation was undertaken to evaluate the development of resistance to thiophanate-methyl in B. cinerea through successive passages and to assess strategies for its management using alternative fungicides. Infected grape fruits were collected from APMC markets and storage houses across Maharashtra, and twenty-five isolates of B. cinerea were obtained. The sensitivity of the isolates to thiophanate-methyl was assessed on Potato Dextrose Agar (PDA). The sensitive isolate (Bc-19) was repeatedly cultured on PDA amended with a sub-lethal concentration of thiophanate-methyl (290.8 µg ml⁻¹). Plates without fungicide served as the control. A 5-mm mycelial disc from the previous passage was transferred to fresh fungicide-amended medium, and radial growth was recorded after eight days. Resistance development was monitored up to the sixth passage, and the percentage increase in mycelial growth over successive passages was used as an indicator of increased resistance. Additional fungicides were evaluated in combination with thiophanate-methyl to determine their effectiveness in managing resistance development.
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