Abstract

Eleven provenances of Eucalyptus were inoculated with 5 monoconidial isolates of C. quinqueseptatum [Calonectria quinqueseptata] varying in morphological, cultural and physiological characteristics. Each provenance showed significant (P0. 01) differences in susceptibility to the different isolates, suggesting the existence of different physiological strains of the pathogen. In addition, the susceptibility ranking of the different provenances to the isolates also differed significantly, indicating a differential interaction between isolates and provenances. Analysis of variance showed that the disease severity of a provenance is mainly governed by the genetically different isolates and also that a close genetic relationship exists between the provenances