Mating Type and Effective Control of Phytophthora colocasiae in Fujian

  Objective   Mating type and fungicides for effective control of Phytophthora colocasiae that caused 2020 taro blight epidemic in Fujian were determined.

  Method   Specimens of diseased taro tissues were collect from the 4 blight-infected regions in Fujian to isolate and identify the pathogen. Based on the morphology, pathogenicity, and sequence homology of ITS-LSU-Ypt1, the pathogenic strains were identified to be of P. colocasiae. Subsequently, mating type and sensitivity to 6 fungicides of the isolates were determined in the laboratory.

  Result  In total, 125 strains were isolated and identified to have caused the epidemic. Out of them, 122 belonged to the A2 mating type and 3 the A1A2 type. The laboratory toxicity test of 6 fungicides on the isolates showed 98% metalaxyl to be the strongest with EC₅₀ of (0.146±0.032) μg·mL⁻¹, while the EC₅₀ of 95% dimethomorph, 98% fluopicolide, and 94% cyazofamid ranged from (0.239±0.011) μg·mL⁻¹ to (0.713±0.088) μg·mL⁻¹ and that of 95% azoxystrobin at (23.447±3.666) μg·mL⁻¹.

  Conclusion  The dominant strains of P. colocasiae that caused the taro blight in Fujian in 2020 were of the A2 mating type and could be best controlled by using 98% metalaxyl, 95% dimethomorph, 98% fluopicolide, or 94% cyazofamid.