Arbuscular mycorrhizal associations and dark septate endophytes in Yacon (Smallanthus sonchifolius) and a wild relative (Smallanthus macroscyphus)

Mycorrhizal associations in Smallanthus sonchifolius (Poepp. & Endl.) H. Robinson (Asteraceae), Yacon, an ancient Andean crop and Smallanthus macroscyphus (Baker ex Martius) A. Grau, wild yacon, a close wild relative are described for the first time. Yacon fibrous roots growing under field conditions have high levels of colonization by arbuscular mycorrhizal fungi (86 %). Other fungi colonizing roots included dark septate endophytes (45 %) and unidentified fungi that are probably saprophytic (25 %) were observed. Only 9% of the samples analyzed were not colonized by any type of fungi. Glomus, Acaulospora, Scutellospora, Gigaspora and Pacispora were the main genera of arbuscular mycorrhiza identified. A similar high degree of mycorrhizal colonization was observed in Smallanthus macroscyphus, in natural populations associated with Juglans australis native forest. The high level of mycorrhizal colonization, the low number of fine absorbing roots and the large roots diameters observed, suggest that both Smallanthus species are likely dependent on mycorrhiza.