Boscalid + Pyraclotrobin Resistance and Expression of Succinate Dehyrogenase Genes (sdhA and sdhB) in Chestnut Blight Fungus Cryphonectria parasitica

Sweet chestnut, Castanea sativa Mill., is a significant species in Turkey. The tree has been encountered with numerous diseases. Chestnut blight, caused by Cryphonectria parasitica (Murrill) M. E. Barr, is one of the most common diseases having spread to every chestnut-growing region. In this study, the effects of Bellis® (25.2% Boscalid + 12.8% Pyraclotrobin), a fungicide commonly used in plant disease control, were evaluated at different doses (10 ppm and 50 ppm) against the chestnut blight agent C. parasitica, which had not been previously studied for its effects in vitro. The isolates included two virulent strains (Cp1_2023, Cp2_2023) and two hypovirulent strains (Cp7_2023, Cp9_2023). The effects of Boscalid + Pyraclotrobin on the mycelial growth of the pathogenic fungus were determined for the first time in vitro, and these effects were detected at the sdhA and sdhB genes expression level. The results showed that the mycelial growth and pathogenicity of C. parasitica isolates in the fungicide-treated medium were consistent with the gene expression profile. Specifically, the virulent Cp1_2023 isolate exhibited higher mycelial growth, pathogenicity, and gene expression levels compared to the other isolate. In conclusion, it is recommended to conduct more detailed studies before using fungicides and to employ them in controlled environments.