Biological Characteristics and Laboratory Toxicity of Sclerotium rolfsii,the Pathogen of Konjak Southern Blight
[Objective]The microorganism type and biological characteristics of the pathogen causing southern blight of konjac were identified,and the highly effective fungicides were screened,so as to provide theoretical basis for planing and implementing the comprehensive field control measures for konjac southern blight.[Method]Tissue isolation and soil dilution methods were used to isolate and purify the pathogen from konjac plants with typical traits of southern blight and the surrounding soil respectively.Pathogens were identified through morphology and molecular systematics.The mycelial growth rate method was used to explore the biological characteristics of the pathogen and the indoor toxicity effected by seven pesticides(difenoconazole,pyraclostrobin,flusilazole,tebuconazole,thifluzamide,diniconazole and propiconazole).[Result]The pathogen of konjac southern blight was Sclerotium rolfsii,whose mycelium grew fastest in OA and PDA media.After three days of cultivation,the colony diameter reached 7 cm,and the mycelium growth rate was 2.33 cm/d.The optimal cultivation temperature was 25-30℃.After three days of cultivation,the colony diameter reached 7.2 cm and the mycelial growth rate was 2.48 cm/d.A weakly acidic environment with a pH of 5-7 was conducive to mycelial growth,with a maximum growth rate of 2.33 cm/d.Peptone as nitrogen source and soluble starch as carbon source were beneficial for the growth of pathogenic hyphae,with growth rates of 2.14 cm/d and 2.43 cm/d,respectively,significantly higher than other treatments.Tebuconazole,diniconazole,thifluzamide,difenoconazole,pyraclostrobin and propiconazole all had good inhibitory effects on pathogen.Among them,tebuconazole had the best preventive effect with an EC50 of 0.101 mg/L,followed by diniconazole,thifluzamide,difenoconazole,pyraclostrobin and propiconazole,with EC50 of 0.165 mg/L,0.185 mg/L,1.026 mg/L,1.842 mg/L,and 2.112 mg/L,respectively.[Conclusion]S.rolfsii is the pathogen that causes southern blight disease of konjac,with a suitable growth temperature of 25-30℃.A weakly acidic and nutrient rich environment is conducive to the growth of pathogenic mycelia.Tebuconazole can effectively inhibit the growth of pathogenic mycelia.
konjakSclerotium rolfsiifungicide screeningbiological characteristicsgrowth rate of mycelialaboratory toxicity
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