This study provides the first report on the diversity of endophytic fungi associated with Calicotome spinosa, offering valuable baseline data for future microbial ecology research on North African medicinal flora. The results reveal a diverse assemblage of culturable endophytic fungi in C. spinosa leaves, predominantly representing taxa from the phylum Ascomycota. This finding is consistent with previous studies, which indicate that Ascomycota comprise approximately 73.1% of known endophytic fungal taxa (Materatski et al. 2018). Members of Ascomycota have been shown to possess a greater number of genes linked to nutrient acquisition, carbohydrate metabolism, competitive ability, and resistance to both abiotic and biotic stressors, compared to other fungal groups (Dos Reis et al. 2023). In addition, many Ascomycota species act as soil saprophytes, capable of degrading complex organic matter and thus playing a central role in ecosystem-level nutrient cycling (Zuo et al. 2022).

Previous studies have documented numerous endophytic fungi associated with Fabaceae plants, including various genera such as Alternaria, Aspergillus, Fusarium, Penicillium, Xylaria, Epicoccum, and Phomopsis, which produce a variety of secondary metabolites (Saini et al. 2025). Consistent with these findings, our study identified several fungal genera reported in Fabaceae endophyte communities, such as Aspergillus, Cladosporium, Chaetomium, Penicillium, and Rosellinia. This overlap highlights that C. spinosa, belonging to the Fabaceae family, might host fungal symbionts with biotechnological applications. The discovery of both widely recognized metabolite-producing taxa and lesser-known or underexplored genera emphasizes the ecological and functional diversity of its endophytic community.

Several fungal genera identified as endophytes in C. spinosa leaves are known for diverse ecological roles, ranging from saprophytism to latent pathogenicity. However, almost none of the fungi detected in the endosphere of C. spinosa are known to be pathogenic to legumes (Sbai et al. 2024); instead, they are recognized as pathogens of other species. Dermatophyte pathogen Trichophyton was found ubiquitously in leaf tissues, although it is rarely reported as a plant endophyte (Kaufman et al. 2007). A notable example of a latent pathogen in our study is Rhizoctonia, the second most abundant genus in C. spinosa leaves. Despite its presence, no disease symptoms were observed, indicating a potential endophytic or latent interaction. Rhizoctonia solani is known to infect over 27 plant families, including important Fabaceae species such as soybeans, peanuts, beans, and alfalfa (Nasimi et al. 2024), while R. medicaginis specifically affects Medicago sativa (Ogoshi 1987). Similarly, Alternaria alternata, the most frequently isolated species in this study, is a common endophyte and occasional pathogen in various plants, including halophytes (Zuo et al. 2022). Its dominance in C. spinosa may be attributed to its adaptability and ecological versatility. Other genera detected, such as Rosellinia and Canariomyces, are also known for their pathogenic potential. Their presence in asymptomatic leaves supports the idea that certain pathogenic fungi may persist as endophytes under nonstressful conditions, possibly gaining a survival advantage in arid or fluctuating environments. Such associations could provide adaptive benefits like thermotolerance and drought resistance, contributing to host survival and ecosystem resilience (Zuo et al. 2022). Penicillium brevicompactum, a xerophilic fungus often associated with indoor environments, and Aspergillus species, which are capable of growth under low water availability (Ndagijimana et al. 2008; Bekoe et al. 2021), further highlight the resilience of the endophytic community in C. spinosa to drought-prone Mediterranean habitats. Schizophyllum commune, typically found on softwood and silage (Tovar-Herrera et al. 2018), was also detected, but in the absence of disease symptoms, it is likely functioning here as a non-pathogenic endophyte.