Field Observations and Inoculation Experiments to Determine the Nature of the Carpophoroids Associated with Entoloma abortivum and Armillaria

Abstract

Carpophoroids traditionally attributed to Entoloma abortivum ("Aborted Entolomas") represent malformed Armillaria fruiting bodies permeated by E. abortivum hyphae, as shown by our field observations and preliminary laboratory work. This contradicts the generally accepted hypothesis that carpophoroids are E. abortivum fruiting bodies colonized by Armillaria. Carpophoroids possess many of the structural characteristics of Armillaria fruiting bodies, including growth and development from rhizomorphs and the production of Armillaria-like spores on basidia. Our inoculation experiments demonstrate the ability of E. abortivum to abort the development of A. tabescens fruiting structures in vitro. In rare instances the introduction of E. abortivum disrupts A. tabescens fruiting structures to the point where they macroscopically resemble immature carpophoroids as observed in nature. If E. abortivum is a parasite of Armillaria species under natural conditions, E. abortivum may contribute to the regulation of Armillaria populations and could be investigated as a candidate for the biological control of destructive Armillaria species. We recommend "Abortive Entoloma" be used as the common name for E. abortivum.

Transcriptomics reveals the putative mycoparasitic strategy of the mushroomEntoloma abortivumon species of the mushroomArmillaria

“…The formation of carpophoroids associated with species of E. abortivum have traditionally been thought to be the result of an Armillaria species attacking and parasitizing Entoloma sporocarps (11), a conclusion drawn based on the fact that Armillaria species are wide-spread forest pathogens (12). However, subsequent studies have shown the opposite: the production of carpophoroids are the result of E. abortivum disrupting the development of Armillaria sporocarps (14). Here, we employed RNA sequencing and differential gene expression analysis on field-collected fungal tissue of each of the three components of this association to better understand the mechanistic basis of this interaction.…”

“…8B). Armillaria mellea has previously been identified as a host of E. abortivum (11,14), but this interaction does not appear specific to just A. mellea. Interestingly, Armillaria species parasitized by E. abortivum appear to be only those present in Eastern North America and Asia (14,37,55).…”

“…The carpophoroid form has traditionally been assumed to be E. abortivum sporocarps that did not develop properly due to parasitism by Armillaria species (11). However, macro-and microscopic studies of carpophoroid field collections determined that carpophoroids actually represent malformed Armillaria sporocarps permeated by E. abortivum hyphae (14).…”

“…Laboratory inoculation experiments showed that E. abortivum interacts with Armillaria sporocarps to disrupt their morphological development (14).…”

Global distribution and richness of Armillaria and related species inferred from public databases and amplicon sequencing datasets

“…Armillaria species in east Asia engage in a form of mycorrhizal relationship known as mycoheterotrophy with species of achlorophyllus orchids in the genera Galeola and Gastrodia (Kikuchi & Yamaji, 2010; Guo et al, 2016). In other examples, Armillaria sporocarps are parasitized by the mushroom-forming species Entoloma abortivum (Lindner Czederpiltz et al, 2001; Koch & Herr, 2021) and potentially also by species in the Ascomycete genus Wynnea (Xu et al, 2019). Lastly, Guyanagaster necrorhizus harbors nitrogen-fixing bacterial species within its sporocarps, which likely facilitates a dispersal mutualism with wood-feeding termites (Koch et al, 2018; Koch et al, 2021).…”