| Tobacco leaf spot of Phoma sorghina is a novel fungal disease in Guangxi,China.In this study,the morphology,ITS,TUB and ACT sequences of the pathogen of the disease were tested.The biological characteristics of the pathogen were also tested.Meanwhile,the fungicides were screened for controlling the disease.The results are as follows.A total thirty-two strains isolated from typical diseased leave of tobacco collected from Guangxi,China were obtained.The symptom on the tobacco leaf inoculated with 6 strains was the same as that on the disease leaf in field.Based on the morphology of colony,pycnidia and conidia,NaOH reaction,the ITS,TUB and ACT sequences,the strain ZS11-2 was identified as Phoma sorghina.The strain ZS11-2 could grow at 5-35℃and pH 3-10,but optimal temperature and pH range were 25 ℃and 5-6,respectively.The pathogen was not strictly required for illumination in the growth process.This strain could use glucose,fructose,sucrose,lactose,maltose,soluble starch,cellulose as carbon sources and sodium nitrate,potassium nitrate,ammonium chloride,ammonium nitrate,ammonium sulfate,alanine and glycine as nitrogen source for its growth,the optimum carbon sources and nitrogen source were fructose and glycine,respectively.The lethal temperature of mycelia was 50℃,10minutes.Strain ZS11-2 could infect rice,corn,sorghum,clover,cowpeas,tomatoes,potato,peppers,eggplant,rape and lettuce.But it could not infect cucumber and melon.Ten fungicides were used to test inhibition effect for Phoma sorghina in vitro.The result showed that prochloraz manganese 400g/L pyrimethanil SC,250 g/L kresoxim pyrazole EC and 450 g/L prochloraz EW were the highest toxicity to the pathogen with EC50 0.57,0.77 and 1.21 mg/L,respectively.The control efficacy of 400g/L pyrimethanil SC on tobacco leaf spot of Phoma sorghina was increased with the enhancement of concentration.In pot trials,400g/L pyrimethanil SC showed the control efficacies of 52.25%,60.13%,respectively,with the concentration of 52.25%and 60.13%.When the concentration increased to 6.36mg/L,the control efficacy of 400g/L pyrimethanil SC was enhanced to 66.67%. |
