Identification,characterization and fungicide screening of the pathogen causing leaf spot on Ligustrum japonicum
Ligustrum japonicum leaf spot occurs universally in Wenhuilu campus of Yangzhou university,Yan-gzhou,Jiangsu,China every spring.The aim of this study was to identify the pathogen species,determine the biological characteristics,and screen out effective pesticides for the prevention and control of the disease.The multiple assays were conducted for the pathogen identification including tissue separation and single-spore purifi-cation,pathogenicity test both in vitro and vivo to fulfill Koch's postulates,and morphological and phylogenetic analysis based on a combined ITS,GAPDH,RPB2 and TEF1 sequence dataset,the biological characterization,and the sensitivity test to the five fungicides.We obtained the purified fungal culture which was further identified as Alternaria alternata,a new pathogen causing leaf spot on L.japonicum.The effect of various carbon and ni-trogen sources for growing of the representative isolate was investigated and A.alternata isolate was suitable for growing on the optimized medium supplied with sucrose,fructose,and potassium nitrate at 25 ℃,pH 9.0.In addition,5 fungicides were assessed on the inhibitory effect against mycelial growth of A.alternata isolate in which azoxystrobin displayed the strongest inhibitory activity with EC50 value of 0.080 6 μg·mL-1,followed by-prochloraz,pyraclostrobin and tebuconazole with EC50 values of 2.272 2 μg·mL-1,3.934 9 μg·mL-1 and 6.400 0μg·mL-1,respectively,while difenoconazole exhibited the least sensitivity at EC50 value of 15.486 0 μg·mL-1.These results indicated that these fungicides could be used for the prevention and control of L.japonicum leaf spot disease.
identification of pathogenbiological characteristicsfungicide screeningAlternaria alternataLigustrum japonicum leaf spot
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万方数据
