The Pathogen Biological Characteristics Of The Pseudocercospora Leaf Spots Of Poplars

This paper systematically study on the pathogen biological characteristics of the cercospora leaf spots of poplars to screen the optimum culture conditions and learn about the basic properties of pathogenic active material. These will provide theoretical basis for the control of the cercospora leaf spots of poplars. Tissue and single spore isolation were conducted to isolate the pathogen, In natural condition, it was easier for pathogen isolation with the conidia than diseased leaf tissue. The pathogen is identified as Pseudocercospora salicina (EⅡ.&Ev.)Deighton according to the disease symptoms, morphological character of fruiting body and its internal transcribed spacer (ITS) sequence of rDNA. Study on the effect of different media, temperature, illumination, pH value, carbon source and nitrogen source on pathogen growth and different nutrient, temperature, pH value and humidity on conidial germination. The optimum culture conditions are oats medium, pH value6～7and culture in darkness at25℃. Soluble starch and beef extract, peptone are better for pathogen growth than other carbon and nitrogen source. The percentage of conidial germination is highest at25℃and pH8, and it increases with the increase of relative humidity. Nitrogen nutrition has greater impact on conidial germination. The toxins in pathogen was extracted and isolated, and the results showed that the toxins of pathogen were small molecules with strong polar. These toxins are hardly soluble in ethanol but soluble in methanol and water which are high polar solvents.