Abstract: ln relation to the pathogenesis of Marssonina leaf blight in natural environment,dynamics of carbohydrates in six Aigeros clones was detected. During the early stage of pathogenesis of Marssonina leaf blight,the concentration of soluble and reducing sugars in leaves of susceptible clones(I-214,P15A and“blane de garonne”)was higher than those resistant ones (I-63,I-69,I-72).The contents of sugars increased in susceptible clones and decreased in resistant ones.On the contrary, the concentration of total carbohydrate in leaves was lower in susceptible clones than in resistant ones during the period. The content of sucrose in stem bark was higher in resistant clones than in susceptible ones.The bark sucrose in autumn was higher than in late summer.