A NEW CERATOCYSTIS SPECIES DEFINED USING MORPHOLOGICAL AND RIBOSOMAL DNA-SEQUENCE COMPARISONS

A Ceratocystis Ell. & Halst. species has recently been reported from A cacia mearnsii De Willd. in South Africa showing symptoms of die-back and gummosis. The fungus was tentatively identified as Ceratocystis fi mbriata Ell. & Halst. that is a well-known and notorious pathogen of m any plants of the world. The fungus from A. mearnsii, however, differs morphologically from authentic C. fimbriata isolates. In this study, isolates from A, mearnsii In South Africa were compared with C. fimbri ata isolates from different geographic areas on the basis of morpholog y and ribosomal RNA (rRNA) sequence data. Morphological comparisons sh owed that the Ceratocystis isolates from A. mearnsii have light-colour ed perithecial bases and divergently arranged ostiolar hyphae compared with entirely black perithecia and convergently arranged ostiolar hyp hae of typical C. fimbriata isolates. Comparisons of rDNA confirmed th e morphological differences and grouped the South African isolates apa rt from C. fimbriata originating from other areas. This important path ogenic fungus is consequently described as new.