Dual-Edged Roles of Fungal Chlamydospores in Plant Protection: Research Progress and Application Potential

Chlamydospores are thick-walled, dormant propagules formed by fungi in response to environmental stress. They play contrasting roles in plant protection: serving as persistent inocula of soil-borne pathogenic fungi that contribute to recurrent disease outbreaks, while also acting as highly stress-resistant propagules for fungal biocontrol formulations. This review examines the ultrastructure, regulation of differentiation, soil survival, and germination behaviour of fungal chlamydospores. It compares diverse survival strategies among pathogenic fungi and discusses natural disease-suppressive mechanisms, including soil fungistasis and germination–lysis. Furthermore, this review highlights the field application advantages of chlamydospores from Trichoderma and nematophagous biocontrol fungi, together with functionally analogous microsclerotia from entomopathogenic fungi. Finally, we identify major challenges in understanding the molecular regulation of chlamydospores, standardizing formulations, and quantitatively characterizing their ecological dynamics in soil. Addressing these challenges will support the sustainable management of soil-borne diseases and the development of fungal biocontrol products.