2024 Volume 66 Pages 37-45
The fungicide sensitivity of 54 strains of gray mold fungus Botrytis cinerea, collected from tomatoes and strawberries in Aichi Prefecture from 2021 to 2022, were tested using primary kidney beans leaves for 16 fungicides, including QoI and SDHI fungicides. The bioassay results indicated that 22 (41%) and 17 (31%) fungal strains were resistant to the QoI fungicide azoxystrobin and pyribencarb, respectively. Moreover, 3 (6%), 2 (4%), and 2 (4%) strains were resistant to the SDHI fungicide penthiopyrad, isofetamid, and pyraziflumid, respectively. Interestingly, 23 (43%) were resistant to pyraclostrobin/boscalid, a combination of QoI and SDHI fungicides, while 8 strains (15%) were resistant to diethofencarb/thiophanate methyl. In addition, structural learning using a Bayesian network with lesion formation inhibition rate reported a probabilistic dependency relationship for QoI fungicides such as pyraclostrobin/boscalid, azoxystrobin, and pyribencarb. Correlation analysis (Spearman’s ρ) to the variation in lesion formation inhibition rate was shown, with 0.68 and 0.62. For SDHI fungicides, correlation analysis was found from penthiopyrad to isofetamid, with 0.5 correlation coefficient. These results suggest the possibility of cross-resistance between fungicides for the same strain in this prefecture.
