McTaggart, Alistair R.Drenth, AndreWingfield, Michael J.O'Dwyer, CeciliaShuey, Louise S.Pegg, Geoff S.2023-11-102023-11-102022-06McTaggart, A.R., Drenth, A., Wingfield, M.J. et al. Epidemic spread of smut fungi (Quambalaria) by sexual reproduction in a native pathosystem. European Journal of Plant Pathology 163, 341–349 (2022). https://doi.org/10.1007/s10658-022-02480-3.0929-1873 (print)1573-8469 (online)10.1007/s10658-022-02480-3http://hdl.handle.net/2263/93227SUPPLEMENTARY TABLE 1 : Sample source location, host, host provenance and host tissue type of all isolates used in the study.SUPPLEMENTARY FIGURE 1 : Neighbour-Net analyses using SplitsTree based on Kosman genetic distance calculated from AFLP data at three epidemic sites: 1A Beaudesert (637 loci), 1B Grafton (600 loci), 1C Traveston (629 loci). Reticulations indicate putative recombinant relationships between individuals. Individuals are coloured based on the clusters identified by the pseudo-F-statistic in analyses of combined sample sites. Corymbia variegata is the host of unlabelled genotypes.DATA AVAILABILITY : All data used in the analyses of genotypic diversity are publicly available here: https://drive.google.com/drive/folders/1Fo5DrgQnNPd8AWSumrsptW_2KaGLj-Y1?usp=sharing.Quambalaria are fungal pathogens of Corymbia, Eucalyptus and related genera of Myrtaceae. They are smut fungi (Ustilaginomycota) described from structures that resemble conidia and conidiophores. Whether these spore forms have asexual or sexual roles in life cycles of Quambalaria is unknown. An epidemic of Q. pitereka destroyed plantations of Corymbia in New South Wales and Queensland (Australia) in 2008. We sampled 177 individuals from three plantations of C. variegata and used AFLPs to test hypotheses that the epidemic was spread by asexual reproduction and dominated by a single genotype. There was high genotypic diversity across ≥600 AFLP loci in the pathogen populations at each plantation, and evidence of sexual reproduction based on neighbour-net analyses and rejection of linkage disequilibrium. The populations were not structured by host or location. Our data did not support a hypothesis of asexual reproduction but instead that Q. pitereka spreads exclusively by sexual reproduction, similar to life cycles of other smut fungi. Epidemics were exacerbated by monocultures of Corymbia established from seed collected from a single provenance. This study showcases an example of an endemic pathogen, Q. pitereka, with a strictly outbreeding life cycle that has caused epidemics when susceptible hosts were planted in large monoculture plantations.en© The Author(s) 2022. Open Access. This article is licensed under a Creative Commons Attribution 4.0 International License.Perennial pathosystemObligate outcrosserForest pathogenPopulation biologySDG-15: Life on landArticle