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First Report of Ceratocystis Wilt of Acacia mearnsii in Uganda

Ceratocystis albofundus, the cause of Ceratocystis wilt of Acacia mearnsii, is known only from South Africa. The only known hosts of this fungus are A. mearnsii, Acacia decurrens, and two species of Protea (1). This pathogen causes stem cankers, xylem discoloration, wilt, and the death of susceptible A. mearnsii trees in South Africa, leading to considerable losses to the forestry industry (1). During a recent survey of forest plantation diseases in Uganda, A. mearnsii trees with “streaked” discoloration of the xylem, typical of Ceratocystis infection, were found in southwestern Uganda. These trees had been damaged mechanically by the harvesting of side branches and/or stems for firewood and construction. Xylem discoloration was spreading through the trees from these wounds. Trees showed typical stem cankers and gummosis, which is associated with C. albofundus infection, as well as foliage wilting. Isolations from infected trees yielded a fungus that was similar morphologically to C. albofundus, with typical hat-shaped ascospores and light-colored perithecial bases (2). Sequencing of the internal transcribed spacer region of the ribosomal RNA operon of Ugandan isolates (CMW5329, CMW5964, GenBank accession no. AF388947) confirmed their identification, grouping them with C. albofundus and separating them from all other Ceratocystis species. This is the first report of C. albofundus from a country other than South Africa. C. albofundus is an important pathogen, and strategies to reduce losses need to be established in Uganda because the aggressiveness of C. albofundus to A. mearnsii has been shown in inoculation experiments (1).

References: (1) Morris et al. Plant Pathol. 42:814, 1993. (2) Wingfield et al. Syst. Appl. Microbiol. 19:191, 1996.