Rephrase the title:This 400-million-year-old fossil is the oldest disease-causing fungus we’ve ever seen!

The ecological significance of fungi cannot be underestimated. Apart from sequestering substantial carbon in soils, they serve as nutritional havens for plant roots seeking a rapid energy boost. Yet, these seemingly benevolent organisms also possess a notorious dark side, causing more plant diseases than any other terrestrial pest.

Scotland’s Natural History Museum has recently disclosed a groundbreaking find within its fossil archives — the earliest disease-causing fungus. Dubbed the Potteromyces asteroxylicola, this fungal plant pathogen is a staggering 407 million years old, and named after Beatrix Potter, the renowned author of ‘Tales of Peter Rabbit’.

Beatrix, a mycology enthusiast beyond her literary contributions, gained acclaim for her adept illustration and scientific research on fungi. Her meticulous studies and detailed drawings, ahead of their time in some instances, have secured her a distinguished position in mycology.

The discovery of Potteromyces is relatively recent. Dr Christine Strullu-Derrien, the lead author, stumbled upon the first specimen in 2015 within fossil samples from Scotland’s pivotal Rhynie Chert site, known for its exceptionally preserved Early Devonian ecosystem. The fungus, unique in its unseen and peculiar reproductive organs, was found infecting a living plant, Asteroxylon mackiei, which in turn began exhibiting dome-shaped growths as a defensive response.

To validate this as a new species, a second specimen was essential. Fortunately, another instance of Potteromyces surfaced in the collections of the National Museums of Scotland, confirming its potential as one of the oldest ancestors of disease-causing fungi, including those affecting the UK’s native ash trees.

Potteromyces not only sheds light on the evolution of fungal groups but also serves as a fitting tribute to Beatrix Potter, whose legacy now extends to one of the earliest fungi known to humanity.

The research findings are published in Nature Communications.