Revisiting the Life Cycle of Dung Fungi, Including Sordaria fimicola

Abstract

Dung fungi, such as Sordaria fimicola, generally reproduce sexually with ascospores discharged from mammalian dung after passage through herbivores. Their life cycle is thought to be obligate to dung, and thus their ascospores in Quaternary sediments have been interpreted as evidence of past mammalian herbivore activity. Reports of dung fungi as endophytes would seem to challenge the view that they are obligate to dung. However, endophyte status is controversial because surface-sterilization protocols could fail to kill dung fungus ascospores stuck to the plant surface. Thus, we first tested the ability of representative isolates of three common genera of dung fungi to affect plant growth and fecundity given that significant effects on plant fitness could not result from ascospores merely stuck to the plant surface. Isolates of S. fimicola, Preussia sp., and Sporormiella sp. reduced growth and fecundity of two of three populations of Bromus tectorum, the host from which they had been isolated. In further work with S. fimicola we showed that inoculations of roots of B. tectorum led to some colonization of aboveground tissues. The same isolate of S. fimicola reproduced sexually on inoculated host plant tissues as well as in dung after passage through sheep, thus demonstrating a facultative rather than an obligate life cycle. Finally, plants inoculated with S. fimicola were not preferred by sheep; preference had been expected if the fungus were obligate to dung. Overall, these findings make us question the assumption that these fungi are obligate to dung.

Fungal Endophytes Control Fusarium graminearum and Reduce Trichothecenes and Zearalenone in Maize

“…Another report documented the reduction of the pathogenicity of the take-all fungus in wheat and the promotion of wheat growth [26]. In another work, this fungus significantly reduced the growth of Bromus tectorum [18]. Here, our findings under greenhouse conditions confirm the potential biocontrol effect of S. fimicola against several pathogens including F. graminearum in maize.…”

“…The beneficial impacts of endophytes on the plant communities is attributed to their ability to enhance plant fitness by conferring abiotic and biotic stress tolerance, increasing biomass, and diminishing water consumption, or decreasing fitness by altering resource allocation. The selected BCAs were all reported previously for their endophytic ability to colonize different plants [18,19], however, they were isolated from soil and maize residues except for Piriformospora strains which were not isolated in the current work [20].…”

“…S. fimicola is an endophyte isolated from soil [26] and several plants [18]. This fungus is associated, but not obligated to the dung of herbivorous animals [18].…”

“…S. fimicola is an endophyte isolated from soil [26] and several plants [18]. This fungus is associated, but not obligated to the dung of herbivorous animals [18]. The biocontrol effect of S. fimicola can be related to multiple modes of action as competition for nutrients and space due to the rapid growth of the fungus and production of certain volatile compounds that may strongly suppress the fungal growth.…”

A Hypothetical Bottleneck in the Plant Microbiome

“…‘Endophyte’ can be seen as a problematic term since surface-sterilization may fail to completely eliminate epiphytes ( Newcombe et al, 2016 ). This fact makes results reported here conservative in the sense that some of the endophytes we report may actually be epiphytes.…”