Resistance of the Ginseng Gray Mold Pathogen, , to Boscalid and Pyraclostrobin Fungicides in China.

Gray mold caused by severely threatens the yield of ginseng (). Various categories of fungicides have been utilized to control gray mold on this crop. In this study, the resistance of 102 isolates of from 11 commercial ginseng-growing regions in China to fungicides was examined. A total of 32.4% were resistant to boscalid, with EC values that ranged from 12.26 to 235.87 μg/ml, and 94.1% were resistant to pyraclostrobin, with EC values that ranged from 5.88 to 487.72 μg/ml. Except for A and D, the amino acid substitutions of P225F, P225L, N230I, H272Y, and H272R in the B subunit from 24 (4 sensitive [S] and 20 resistant [R]), 5 (1 S and 4 R), 1 (S), 1 (R), and 8 (4 S and 4 R) strains, respectively, and the concurrent amino acid substitutions of G85A + I93V + M158V + V168I in the C subunit from 5 (4 S and 1 R) strains were identified. A G143A substitution in cytochrome b was identified in 96 isolates that were resistant to pyraclostrobin and three that were sensitive to it. The Bcbi-143/144 intron was identified in the other three isolates sensitive to pyraclostrobin, but it was absent in the isolates that harbored the G143A mutation. The results showed that the populations of on ginseng have developed strong resistance to pyraclostrobin. Therefore, it is not recommended to continue using this fungicide to control gray mold on . Boscalid is still effective against most isolates. However, to prevent fungicide resistance, it is recommended to use a mixture of boscalid with other categories of fungicides.