Abstract
Austropuccinia psidii is a rust fungus that has expanded its known geographic distribution and host range on Myrtaceae. Invasions by rust fungi are often caused by asexual urediniospores that give rise to populations with low genotypic diversity. Recently it was shown that basidiospores, the gametic spores of A. psidii, were able to infect species of Myrtaceae under controlled conditions. The present study tested the hypothesis that sexual reproduction occurs through infection of Myrtaceae by basidiospores of A. psidii in recently invasive populations from New Zealand and South Africa. We provided three lines of evidence to test this hypothesis: i) presence of a sexual stage, ii) high genotypic diversity within an invasive population, and iii) no genetic linkage between microsatellite markers in multilocus genotypes. Our results provide evidence that invasions of A. psidii are caused by both urediniospores that spread clonal genotypes, and teliospores that produce recombinant basidiospores, which infect Myrtaceae. We reject the hypothesis that field infections of A. psidii are only caused by asexual urediniospores, and support that sexual reproduction occurs in invasive populations and may accelerate adaptation to environmental change.
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Acknowledgements
We are grateful to Kate and Graham Grieve (Custodians of Rare and Endangered Wildflowers, CREW), as well as Jackie Cossey, Izette Greyling, Giovanni Sale, Christo van Zyl and Henk du Plessis for providing or assisting in collection of samples for this study. This work is based on research partially supported by the Tree Protection Co-operative Programme (TPCP) and the National Research Foundation of South Africa (Grant specific unique reference numbers UID 78566 and UID 83924) and the DST-NRF Centre of Excellence in Tree Health Biotechnology (CTHB). The grant holders acknowledge that opinions, findings and conclusions or recommendations expressed in any publication generated by NRF supported research are that of the authors and that the NRF accepts no liability whatsoever in this regard. ARM acknowledges the University of Queensland Development Fellowships (UQFEL1718905) and support from the Department of the Environment and Energy under the Australian Biological Resources Study (grant number RG18-43). This work was partly funded by the New Zealand Ministry of Business, Innovation and Employment (C09X1806), and the Australian Plant Biosecurity Science Foundation (PBSF018). We thank Luke Barrett and eight anonymous reviewers who have helped improve previous submissions of this manuscript.
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McTaggart, A.R., du Plessis, E., Roux, J. et al. Sexual reproduction in populations of Austropuccinia psidii. Eur J Plant Pathol 156, 537–545 (2020). https://doi.org/10.1007/s10658-019-01903-y
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DOI: https://doi.org/10.1007/s10658-019-01903-y