Control Fungicide Screening and Resistance Monitoring to Thifluzamide of Rice Sheath Blight Pathogen Rhizoctonia solani in Heilongjiang Province

摘要

In recent years,the prevalence of rice sheath blight caused by Rhizoctonia solani has significantly increased in Heilongjiang Province.Chemical control has become the primary control method.To cope with this,a novel mycelium growth rate method was employed to assess the toxicity of 13 fungicides,including a combination of 45% prochloraz and 125 g·mL^-1 epoxiconazole,against R.solani.Additionally,the resistance of 99 R.solani strains to thifluzamide across various regions was also evaluated.The findings indicated that 75% trifloxystrobin-tebuconazole exhibited the most effective inhibitory effect,with an effective inhibitory medium concentration (EC₅₀) value of 0.0101 μg·mL^-1.The EC₅₀ values for 20% prothioconazole,125 g·mL^-1 epoxiconazole,24% thifluzamide,and 50% hexaconazole were all less than 10 μg·mL^-1,indicating a better inhibitory effect on R.solani.The strongest synergistic effect was noted in the mixture of prochloraz and epoxiconazole at a 1:2 ratio,resulting in an EC₅₀ value of 2.9917 μg·mL^-1,and a co-toxicity coefficient of 213.38.Among the 34 strains from Harbin City,the average EC₅₀ value was 196.9341 μg·mL^-1 indicating the highest susceptiblility to thifluzamide.Conversely,15 strains from Shuangyashan City exhibited an average EC₅₀ value of 364.7323 μg·mL^-1,reflecting the lowest sensitivity to thifluzamide.The sensitivity baseline EC₅₀ value for R.solani was 253.8854 μg·mL^-1,with an overall resistance level between 0.1567 and 3.3292,indicating that the resistance level of R.solani in Heilongjiang Province remained low.Therefore,R.solani was still sensitive to thifluzamide in most areas of Heilongjiang Province,but there was a certain risk of resistance in Qitaihe City,which needed to be continuously monitored.At the same time,this study might provide a theoretical foundation for enhancing the prevention and management of the rice sheath blight.

关键词

rice sheath blight / Rhizoctonia solani / fungicide screening / thifluzamide / resistance monitoring