Biological characters and rDNA ITS sequences of pathogen of poplar leaf blight

DNA was extracted from the strain of pathogen of poplar leaf blight using a modified CTAB method. ITS sequence (601bp) was initially amplified from the pathogen by using the universal primers ITS1 and ITS4 (registered No. DQ011257). Comparing to the nucleotide sequences acquired from GenBank database, the strain is clustered into the homogeneity with Alternaria alternate (AY787684) and Alternaria alternate (AY354228), with a homology of 98%, thus the strain was checked as Alternaria alternata (Fr.) Keissler. The optimal conditions for conidia germination and mycelium growth of the pathogen were tested. The optimal temperature for conidia germinating and mycelium growth is 25°C, and the optimal pH value is 6. Mycelium grows rather slowly at 10 °C and 30 °C and growth stops at above 35 °C. Among the six culture mediums tested, PDA + poplar leaf juice medium is most favorable for mycelium growth.