COMPARATIVE STUDIES OF ISOLATES OF MARSSONINA BRUNNEA IN CHINA Active Oxygen Release and Membrane Lipid Peroxidation in the Interaction of Marssonina brunnea Elicitor and Poplar Suspension Cell Characteristics of ITS2 Secondary Structure of Marssonina brunnea Two Formae Speciales Study on the Disease Resistance of New Poplar Cultivars to Trunk Cancer, Dothiorella gregaria, and Leaf Black Spot, Marssonina brunnea