Revision of Bionectriaceae and acremonium-like fungi in Hypocreales

Abstract

Bionectriaceae and acremonium-like fungi are globally distributed and ecologically versatile, inhabiting soil, wood, litter, plant tissues, insect hosts, and other substrates. They function as saprotrophs, endophytes, pathogens, mycoparasites, and entomopathogens, with considerable industrial, agricultural, and pharmaceutical relevance through roles in biocontrol, enzyme production, and secondary metabolite synthesis. Chapter 1 reviews Hypocreales, an order encompassing Bionectriaceae and most acremonium-like fungi, and highlights its taxonomic history and morphological characteristics. Acremonium-like fungi, characterised by reduced morphologies, are introduced with emphasis on classification challenges and diversity. The chapter also reviews Bionectriaceae, its evolutionary history, and the diversity of sexual and asexual morphs. Particular attention is given to Clonostachys and Acremonium, genera of agroforestry and industrial importance. Finally, the aims and structure of this thesis are outlined. Chapter 2 investigates Clonostachys, the type genus of Bionectriaceae, whose type species, C. rosea, is widely recognised as an effective biocontrol agent. Multilocus phylogenies combined with morphological analyses produced a well-resolved framework and clarified species boundaries. This study describes 24 new species and 10 new combinations. Chapter 3 expands the analysis to the family Bionectriaceae. Despite ecological and industrial importance, the family has remained taxonomically unclear. Integrating morphological and phylogenetic data, this study recognises 50 genera and 352 species, and proposes seven new genera, 35 new species, and nine new combinations, significantly redefining family boundaries. Acremonium-like fungi are cosmopolitan and function as saprobes, pathogens, endophytes, and mycoparasites, with importance in agriculture, biotechnology, and medicine. Their classification is problematic due to overlapping micromorphologies. Chapter 4 reassesses isolates labelled as “Acremonium sp.” and related taxa using multilocus phylogeny and morphology. Results revealed 148 species across 17 families of Hypocreales and one family, Trichosphaeriaceae, in Trichosphaeriales. Consistent with Hou et al. (2023), most acremonium-like fungi belong to Hypocreales, with Acremonium s. str. restricted to Bionectriaceae. Two new families, seven new genera, 34 new species, and three new combinations are proposed. In Chapter 5 the key findings of Chapters 2–4 are highlighted, and the positive and negative impact of Bionectriaceae and acremonium-like fungi on agriculture and human health discussed. This chapter also highlights the limitations and challenges in resolving phylogenetic complexity, gaps in molecular data for some genera of Bionectriaceae, and the limited genomic resources available for Clonostachys research despite its potential for biological control. It also suggests directions for future research. With the ongoing advancement of molecular and morphological techniques, research on these fungal groups is expected to yield novel insights with far-reaching implications for both fundamental science and practical applications in agriculture, biotechnology, medicine, and ecosystem management.