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Wang, Yen-Wen [1], Elmore, Holly [2], Golan, Jacob [1], Pringle, Anne [3].

Haploid fruiting in the invasive range of the heterothallic fungus Amanita phalloides.

Haploid fruiting implies the development of sporocarps generated without mating in a heterothallic basidiomycete fungus. Haploid fruiting has been reported in multiple species in laboratories and is either induced or occurs spontaneously, but haploid mushrooms have not been identified in nature. The ability to develop haploid sporocarps may facilitate invasions because fewer mates are available in a novel habitat typically. Amanita phalloides is an appealing subject for studying haploid fruiting as it has successfully established or invaded globally and also caused numerous poisonings. Our laboratory has sequenced 86 A. phalloides sporocarps from both an invasive range (California) and native ranges (Europe). Unexpectedly, we identified two individuals with estimated heterozygosity ten times lower than the estimates for other individuals. We confirmed that these two individuals are genetically haploid through k-mer and allele depth frequency analyses. To verify these two individuals are not undergoing intensive inbreeding between two haploid mycelia carrying different mating type genes, we investigated the mating type loci-homeodomain (HD) and pheromone receptor (PR) loci-within A. phalloides. The high genetic diversity in the HD locus but low diversity in the PR locus suggests that A. phalloides is a bipolar heterothallic species. However, the haploid fruiting individuals have zero heterozygosity in the HD locus, supporting our hypothesis. Surprisingly, kinship analyses suggest these two individuals are regularly mating with other haploid mycelia, indicating they are not undergoing speciation events. One genotype appears to have persisted for at least for 20 years. The mycelia of haploid sporocarps can be binucleate or uninucleate while the mycelia of genetically diploid sporocarps are binucleate only. We tentatively hypothesize the haploid fruiting bodies are the results of self-compatible HD genes and that flexible mating systems aid the invasion of A. phalloides.

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1 - University of Wisconsin-Madison, Botany, B101 Birge Hall, 430 Lincoln Drive, Madison, Wisconsin, 53706, United States
2 - Harvard University, Organismic and Evolutionary Biology, 26 Oxford Street Cambridge, MA, 02138, USA
3 - University of Wisconsin-Madison, Botany and Bacteriology, B101 Birge Hall, 430 Lincoln Drive, Madison, Wisconsin, 53706, United States

plastid genome
Ectomycorrhizal fungi
Population genomics

Presentation Type: Oral Paper
Session: MY5, Mycology: Systematics, Biodiversity, and Evolution
Location: /
Date: Wednesday, July 21st, 2021
Time: 3:00 PM(EDT)
Number: MY5001
Abstract ID:245
Candidate for Awards:MSA Best Oral Presentation Award by a Graduate Student

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