Unique clones of the pitch canker fungus, Fusarium circinatum, associated with a new disease outbreak in South Africa
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Pitch canker of pines is caused by the fungus Fusarium circinatum. In South Africa, this pathogen has mostly been a nursery problem. From 2005, however, outbreaks of pitch canker have been reported from established Pinus radiata and P. greggii in the Western and Eastern Cape Provinces. Most recently, pitch canker-like symptoms were observed on 10-year-old P. greggii trees in a plantation in the midlands of the KwaZulu-Natal (KZN) Province. The aim of this study was to: (i) identify the causal agent of the observed symptoms, (ii) determine the genetic diversity, and (iii) the mode of reproduction of this fungal population. Furthermore, the aggressiveness of isolates from these trees was compared with that of isolates obtained previously from P. patula in South Africa. Isolates from the P. greggii trees in KZN were confirmed as F. circinatum based on both morphology and DNA sequence analyses. Microsatellite marker analyses revealed the presence of five genotypes of F. circinatum, not previously reported from other plantations in South Africa, with one of these genotypes being dominant. These genotypes were all pathogenic to P. patula and P. elliottii. No evidence of sexual reproduction was detected in the KZN population of the fungus. This was consistent with the fact that isolates from P. greggii were all of the MAT-2 mating type, in contrast to previously collected isolates from across South Africa that included both mating types. The results suggest that the outbreak of pitch canker on P. greggii in KZN represents a separate introduction of F. circinatum into the region with important implications for managing the disease.
KeywordsMating type Microsatellite analyses Pinus greggii Population diversity
We are grateful to members of the Tree Protection Cooperative Programme (TPCP) and Department of Science and Technology (DST)/National Research Foundation (NRF) and the Centre of Excellence in Tree Health Biotechnology (CTHB) of South Africa, for providing funding and support for this study. The assistance of foresters in the identification of the site and assistance with sampling in Demagtenberg, KwaZulu-Natal Province is appreciated.
- Burnett, J. H. (2003). Fungal populations and species. Oxford university press on demand. Oxford: United Kingdom.Google Scholar
- DAFF (Department of Agriculture, Forestry and Fisheries), (2009). Report on commercial timber resources and primary roundwood processing in South Africa 2008/9.Google Scholar
- Morariu, V. I., Srinivasan, B. V., Raykar, V. C., Duraiswami, R., & Davis, L. S. (2008). Automatic online tuning for fast Gaussian summation. Advances in Neural Information Processing Systems, 21, 1113–1120.Google Scholar
- Nelson, P. E., Toussoun, T. A., & Marasas, W. F. O. (1983). Fusarium species: an illustrated manual of identification. University Park, PA: Pennsylvania State University Press.Google Scholar
- Schulze, R. E., & Maharaj, M. (1997). South African atlas of agrohydrology and-climatology. Pretoria, South Africa: Water Research Commission.Google Scholar
- Schweigkofler, W., O’Donnell, K., & Garbelotto, M. (2004). Detection and quantification of airborne conidia of Fusarium circinatum, the causal agent of pine pitch canker, from two California sites by using a real-time PCR approach combined with a simple spore trapping method. Applied and Environmental Microbiology, 70, 3512–3520.CrossRefPubMedPubMedCentralGoogle Scholar
- Steenkamp, E. T., Wingfield, B. D., Coutinho, T. A., Zeller, K. A., Wingfield, M. J., Marasas, W. F. O., & Leslie, J. F. (2000). PCR-based identification of MAT-1 and MAT-2 in the Gibberella fujikuroi species complex. Applied and Environmental Microbiology, 66, 4378–4382.CrossRefPubMedPubMedCentralGoogle Scholar
- Yeh F.C., Yang, R. C., & Boyle, T. (1999). POPEGENE version 1.31 Microsoft windows based freeware for population genetic analysis. Alberta. [https://www.ualberta.ca/~fyeh/popgene.pdf]. Accessed 22 October 2015.