Colonization of intraradical structures of arbuscular mycorrhizal fungi by dark septate endophytic fungi

Abstract Extraradical spores of arbuscular mycorrhizal (AM) fungi are often parasitized by a wide range of soil microorganisms. However, reports on the parasitization of intraradical structures of AM fungi are very rare. While examining AM colonization in roots of Cuminum cyminum and Sambucus nigra growing in the medicinal plants garden of the Centre of Medicinal Plants Research in Homeopathy of the Nilgiris, we found that AM fungal hyphal coils, arbusculate coils, vesicles, and intraradical spores are colonized by dark septate endophytic (DSE) fungi which were co-occurring with AM fungi. The AM fungal hyphae were significantly wider than the DSE fungi. Colonization of different AM fungal structures significantly varied between the two plant species. Moreover, the percentage of colonized AM fungal structures was linearly correlated to the abundance of these structures. The colonization of the intraradical structures of AM fungi is illustrated and the significance of this phenomenon needs further elucidation.