Innate traits of Pinaceae-specific ectomycorrhizal symbiont Suillus luteus that differentially associates with arbuscular mycorrhizal broad-leaved trees in vitro

• Suillus luteus associates solely with Pinaceae as an ectomycorrhizal symbiont in the wild.
• Prunus speciosa and Cedrela odorata naturally harbor arbuscular mycorrhizal fungi.
• S. luteus established root endophyte symbioses in vitro with P. speciosa.
• S. luteus colonized only the surface of the exodermis of C. odorata.
• S. luteus markedly promoted the growth of P. speciosa, but not C. odorata.

Suillus luteus (Boletales, Agaricomycetes) associates solely with Pinaceae species as an ectomycorrhizal symbiont in the Northern Hemisphere. Prunus speciosa (Rosaceae) and Cedrela odorata (Meliaceae) naturally harbor arbuscular mycorrhizal fungi. The present study documents that S. luteus establishes root endophyte symbioses in vitro with somatic Prunus speciosa; however, it does not penetrate root tissues of somatic Cedrela odorata. With P. speciosa, the hyphae of S. luteus were heavily entangled in the intercellular space, unlike the rather straight hyphae of Tricholoma matsutake (Agaricales, Agaricomycetes). With C. odorata, S. luteus colonized only the surface of the exodermis and exhibited dark-brown mycorrhiza-like morphology. Prunus speciosa associated with S. luteus grew significantly better than that without the fungus, but C. odorata did not show significant beneficial effects when growing with the fungus. The data indicate that apparent Pinaceae-specific ectomycorrhizal fungi associate with arbuscular mycorrhizal broad-leaved plants in vitro, although the physical characteristics of the interactions vary depending upon the plant and fungal species.