High levels of genetic diversity and cryptic recombination is widespread in introduced Diplodia pinea populations
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Introduced populations of organisms typically have reduced diversity compared to those that are native. It is, therefore, unusual that introduced populations of the fungal tree pathogen Diplodia pinea have been shown to have high levels of genetic diversity, even surpassing diversity in some native regions. This is thought to be due to multiple introductions over time or the existence of a cryptic and yet undiscovered sexual cycle. In this study, we consider whether populations of D. pinea in Southern Hemisphere countries have similar patterns of diversity, share some level of genetic identity and how they might be influenced by sexual recombination. A total of 173 isolates from Argentina, Australia, Ethiopia and South Africa were characterized using 12 microsatellite markers. The results show that all these populations have high gene and genotype diversities, with the Australian population having the lowest diversity. Very few private alleles were found, suggesting that isolates from different countries might share a source of introduction. However, based on allele distribution and frequency, each of the populations appeared to be evolving independently. The results showed that in all but the Australian population, alleles are randomly associated, suggesting that widespread sexual recombination has influenced population structure.
KeywordsDiplodia pinea Simple sequence repeat marker Genetic diversity Cryptic sex
This research was financially supported by the DST/NRF Centre of Excellence in Tree Health Biotechnology (CTHB), members of the Tree Protection Co-operative Program (TPCP) and the International Foundation for Sciences, Stockholm, Sweden, through a grant to Wubetu Bihon.
- Agapow PM, Burt A (2000) ‘Multilocus 1.2’. Department of Biology, Imperial College, AscotGoogle Scholar
- Bihon W, Slippers B, Burgess T, Wingfield MJ, Wingfield BD (2011b) Diverse sources of infection and cryptic recombination revealed in South African Diplodia pinea populations. Fungal Biol (submitted)Google Scholar
- Bihon W, Slippers B, Burgess T, Wingfield MJ, Wingfield BD (2010) Sources of Diplodia pinea endophytic infections in Pinus patula and P. radiata seedlings in South Africa. Forest Pathol. doi: 10.1111/j.1439-0329.2010.00691.x
- Burgess TI, Wingfield MJ (2002) Quarantine is important in restricting the spread of exotic seed-borne tree pathogens in the southern hemisphere. Int Forest Rev 4:56–65Google Scholar
- Groenewald M, Linde CC, Groenewald JZ, Crous PW (2008) Indirect evidence for sexual reproduction in Cercospora beticola populations from sugar beet. Plant Pathol 57:25–32Google Scholar
- Halliburton R (2004) Introduction to population genetics. Pearson Education, Inc., USAGoogle Scholar
- Sutton BC (1980) The Coelomycetes. Commonwealth Mycological Institute, KewGoogle Scholar
- Swart WJ, Knox-Davis PS, Wingfield MJ (1985) Sphaeiopsis sapinea, with special reference to its occurrence on Pinus spp. in South Africa. S Afr For J 35:1–8Google Scholar
- Weir BS (1997) Genetic data analysis II. Sinauer Associates Inc, SunderlandGoogle Scholar
- Wingfield MJ, Knox-Davies PS (1980) Association of Diplodia pinea with a root disease of pines in South Africa. Plant Dis 64:22–223Google Scholar
- Yeh FC, Yang RC, Boyle T (1999) POPEGENE version 1.31 Microsoft windows based freeware for population genetic analysis. AlbertaGoogle Scholar