First report of Chrysoporthe cubensis from Eucalyptus in Ghana
1 Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Pretoria 0002, South Africa
2 Forestry Research Institute of Ghana (FORIG), Kumasi, Ghana
Accepted: 01 Dec 2009
During disease surveys of Eucalyptus grandis, E. camaldulensis and E. dagambae in the Ashanti, Central and Eastern Provinces of Ghana in February 2007 stem cankers on mature E. dagambae, resembling that caused by species of Chrysoporthe, were observed in a single compartment near Kumasi. Infection was visible only as stem cankers, characterized by cracked bark, mostly at the bases of trees, bearing long necked fungal fruiting bodies, visible with the naked eye or a hand lens. Some cankers girdled the entire tree. Orange spore masses were transferred aseptically from the tips of the fruiting bodies to malt extract agar (MEA) plates. Fungal isolates were identified using DNA sequence data of the rDNA (ITS, 5.8S) (GenBank Accession No. GQ292541) and beta tubulin gene regions (GU014577). Isolates from Ghana represent C. cubensis, grouping with isolates in the South American clade and similar to isolates from the Republic of Congo and Cameroon (Gryzenhout et al. 2004; Roux et al. 2003). This is in contrast to C. cubensis isolates from East Africa which group in the Asian clade (Nakabonge et al. 2006).
Sixteen isolates of C. cubensis, obtained from 16 separate trees, were assessed for their phenotypic diversity. This was done by vegetative compatibility grouping (VCG) of single hyphal tip isolates on oatmeal agar (OA). All isolates, except one, resided in a single VCG type (Fig. 1d), supporting suggestions that C. cubensis in West Africa has been introduced (Wingfield 2003). Two isolates of C. cubensis from Ghana were inoculated into the stems of ten trees each of a one-year-old E. grandis clone in the greenhouse. After six weeks lesions had formed in the bark and cambium (Fig. 1a, 1b), stretching into the xylem of inoculated trees (Fig. 1c). C. cubensis was successfully re-isolated. No lesions were formed in the control inoculations (Fig. 1a). This is the first report of C. cubensis from Ghana and attacking E. dagambae, expanding the host and geographic range of this possibly introduced pathogen (Nakabonge et al. 2006) in Africa.
The National Research Foundation of South Africa (NRF) funded the research.
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This report was formally published in Plant Pathology
©2009 The Authors