Identification of the pathogen causing leaf spot on watermelon and fungicide screening in vitro
A kind of watermelon leaf spot disease was found in Pudong district,Shanghai.The isolates were obtained from diseased samples by tissue isolation method.Pathogenicity of the isolate SHCCC01 was verified by Koch's postulates.The pathogen was identified by morphology,biological characteristics,and multilocus phylogenetic analysis based on the internal transcribed spacer(ITS),histone(His),translation elongation factor 1α(TEF1-α)and actin(Act).The results showed that the pathogen of the watermelon leaf spot disease was Cercospora citrullina.Among the ten tested fungicides,fluazinam,hexaconazole,epoxiconazole and tebuconazole showed strong inhibition to hyphal growth of C.citrullina isolate SHCCC01 with the EC50 value of 0.375 2,0.575 4,1.472 3 and 1.890 2 μg/mL,respectively.These results provide important theoretical basis for control of watermelon Cercospora leaf spot disease and registration of fungicides.
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