Emergence of the Ug99 Lineage of the Wheat Stem Rust Pathogen Through Somatic Hybridisation
ARTICLE https://doi.org/10.1038/s41467-019-12927-7 OPEN Emergence of the Ug99 lineage of the wheat stem rust pathogen through somatic hybridisation Feng Li 1,10, Narayana M. Upadhyaya 2,10, Jana Sperschneider3, Oadi Matny 1, Hoa Nguyen-Phuc 1, Rohit Mago2, Castle Raley4,8, Marisa E. Miller1,9, Kevin A.T. Silverstein 5, Eva Henningsen 1, Cory D. Hirsch 1, Botma Visser6, Zacharias A. Pretorius6, Brian J. Steffenson 1, Benjamin Schwessinger7, Peter N. Dodds 2* & Melania Figueroa 2* 1234567890():,; Parasexuality contributes to diversity and adaptive evolution of haploid (monokaryotic) fungi. However, non-sexual genetic exchange mechanisms are not defined in dikaryotic fungi (containing two distinct haploid nuclei). Newly emerged strains of the wheat stem rust pathogen, Puccinia graminis f. sp. tritici (Pgt), such as Ug99, are a major threat to global food security. Here, we provide genomics-based evidence supporting that Ug99 arose by somatic hybridisation and nuclear exchange between dikaryons. Fully haplotype-resolved genome assembly and DNA proximity analysis reveal that Ug99 shares one haploid nucleus genotype with a much older African lineage of Pgt, with no recombination or chromosome reassort- ment. These findings indicate that nuclear exchange between dikaryotes can generate genetic diversity and facilitate the emergence of new lineages in asexual fungal populations. 1 Department of Plant Pathology, University of Minnesota, St. Paul, MN 55108, USA. 2 Commonwealth Scientific and Industrial Research Organisation, Agriculture and Food, Canberra ACT 2601, Australia. 3 Biological Data Science Institute, The Australian National University, Canberra ACT 2601, Australia. 4 Leidos Biomedical Research, Frederick, MD 21702, USA. 5 Minnesota Supercomputing Institute, Minneapolis, MN 55455, USA.
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