Exploring Multifaceted Roles of Bambusicolous Apiospora in Phyllostachys bambusoides.

Bamboo plays a crucial role in mitigating climate change. Among various microorganisms inhabiting bamboo, Apiospora is a common bambusicolous fungus that induces black spots, functioning either as a saprobe or as a plant pathogen. However, the diversity and ecological roles of Apiospora as an endophyte in bamboo remain poorly understood. This study explored the diversity and ecological functions of bambusicolous Apiospora in Phyllostachys bambusoides forests. Bamboo samples representing different stages-young (1-year-old, without black spots), mature (aged 3 years, few black spots), and dead (with many black spots)-were collected. Mycobiome analyses across different tissues (culm, leaf, root) and environmental samples (forest soil) revealed diverse Apiospora species throughout the bamboo lifecycle. Notably, Apiospora hysterina emerged as a prevalent endophyte, inhabiting not only mature but also younger, healthier bamboo stages. Biological activity assays, including antioxidant, antifungal, and plant hormone tests, indicated that A. hysterina exhibits potential mutualistic interactions beneficial to bamboo. Conversely, genomic analyses of carbohydrate-active enzyme profiles, effector/virulence factors, and putative biosynthetic gene clusters suggested potential pathogenic capabilities that may involve secondary metabolites, though functional validation is required. These findings reveal the widespread presence of Apiospora species as endophytes from the early to senescent bamboo stages, highlighting A. hysterina's dual capacity as a symbiont and pathogen. Our study underscores the complexity of bambusicolous Apiospora's ecological roles, emphasizing the need for further investigation into its interactions with bamboo ecosystems.