Abstract
The aim of this study was to evaluate the resistance of Botrytis cinerea to the fungicides currently used for its control in Brazil. Isolates of the fungus were collected from different strawberry-producing fields in the states of Espirito Santo, Minas Gerais, and Sao Paulo, Brazil. First, a total of 183 isolates were identified at the species level using specific primers for the glyceraldehyde-3-phosphate dehydrogenase (G3PDH) gene. The isolates were grown on potato dextrose agar (PDA) containing the fungicides procymidone, iprodione, and thiophanate-methyl in different concentrations: 0.0 (control), 0.1; 1.0; 10.0; 100.0 and 1,000.0 μg∙mL−1. The percentage of mycelial growth inhibition was used to determine the effective concentration of the fungicide that was able to inhibit colony growth by 50% (EC50). Approximately 25.7% of the isolates were resistant to iprodione, 53.0% were resistant to procymidone, and 93.0% were resistant to thiophanate-methyl. Moreover, crossresistance and multiple resistance were verified, with 19.7% of the isolates showing resistance to 3 fungicides simultaneously. This finding explains the ineffectiveness of fungicides application to control gray mold in strawberry fields in Brazil and highlights the need for new strategies to manage this disease in the culture.
Highlights
Gray mold caused by the fungus Botrytis cinerea Pers. ex Fries is a very common disease, affecting approximately 200 species of different botanical families, among them fruits, vegetables, ornamental, and wild plants (Elad et al 2007; Williamson et al 2007)
25.7% of the isolates were resistant to iprodione, 53.0% were resistant to procymidone, and 93.0% were resistant to thiophanate-methyl
Crossresistance and multiple resistance were verified, with 19.7% of the isolates showing resistance to 3 fungicides simultaneously. This finding explains the ineffectiveness of fungicides application to control gray mold in strawberry fields in Brazil and highlights the need for new strategies to manage this disease in the culture
Summary
Gray mold caused by the fungus Botrytis cinerea Pers. ex Fries is a very common disease, affecting approximately 200 species of different botanical families, among them fruits, vegetables, ornamental, and wild plants (Elad et al 2007; Williamson et al 2007). Gray mold is considered the main disease in strawberry (Fragaria x Ananassa) production (Maas 1998; Costa et al 2014) because the fungus can infect leaves, stems, flowers, and fruits at any stage of development. The fungus can infect all parts of the plant, the damage is more common during the production phase when the pathogen infects flowers (Bristow et al 1986; Maas 1998; Elad et al 2007; Costa et al 2014). Only 3 groups of fungicides are registered by the Ministério da Agricultura, Pecuária e Abastecimento (MAPA) for strawberry gray mold control in Brazil: Dicarboxamides, Methyl Benzimidazole Carbamate (MBC), and Anilinopyrimidine (Brasil 2016)
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