Physiologic specialisation in the hyperparasitism of races of Melampsora larici-populina by isolates of Cladosporium tenuissimum.

Three isolates of Cladosporium tenuissimum were prepared by culturing a field isolate of this organism separately on three races of Melampsora larici-populina. In a subsequent experiment, the production of uredinia by these three races on three cultivars of Populus X euramericana was usually lowest in the presence of the isolate of C. tenuissimum which had been cultured on the particular race. This apparent adaptation of the isolates of the hyperparasite to particular races of the rust, i. e. "physiologic specialisation" in the relationship, is confirmed by the significant race x C. tenuissimum isolate term in the ANOVA. [ABSTRACT FROM AUTHOR]