New Disease Reports
New Disease Reports (2009) 20, 21.
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First report of Chrysoporthe cubensis from Eucalyptus in Ghana

J. Roux 1* and M. Apetorgbor 2

*Jolanda.roux@fabi.up.ac.za

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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.

Figure1+
Figure 1: (a) Lesions produced by Chrysoporthe cubensis isolated from E. dagambae in Ghana on E. grandis (left) and control inoculation (right); (b) xylem lesion produced by C. cubensis on E. grandis; (c) xylem discolouration produced by C. cubensis from Ghana after six weeks on one-year-old E. grandis; (d) vegetative compatibility results showing single isolate of different VCGs
Figure 1: (a) Lesions produced by Chrysoporthe cubensis isolated from E. dagambae in Ghana on E. grandis (left) and control inoculation (right); (b) xylem lesion produced by C. cubensis on E. grandis; (c) xylem discolouration produced by C. cubensis from Ghana after six weeks on one-year-old E. grandis; (d) vegetative compatibility results showing single isolate of different VCGs

Acknowledgements

The National Research Foundation of South Africa (NRF) funded the research.

References

  1. Gryzenhout M, Myburg H, van der Merwe NA, Wingfield BD, Wingfield MJ, 2004. Chrysoporthe, a new genus to accommodate Cryphonectria cubensis. Studies in Mycology 50, 119-142.
  2. Nakabonge G, Roux J, Gryzenhout M, Wingfield MJ, 2006. Distribution of Chrysoporthe canker pathogens on Eucalyptus and Syzygium spp. in Eastern and Southern Africa . Plant Disease 90, 734-740.
  3. Roux J, Myburg H, Wingfield BD, Wingfield MJ, 2003. Biological and phylogenetic analyses suggest that two Cryphonectria spp. cause cankers of Eucalyptus in Africa . Plant Disease 87, 1329-1332.
  4. Wingfield MJ, 2003. Daniel McAlpine Memorial Lecture. Increasing threat of disease to exotic plantation forests in the Southern hemisphere: lessons from Cryphonectria canker. Australasian Plant Pathology 32, 133-139.
This report was formally published in Plant Pathology

©2009 The Authors