LAUSR

We investigated the effects of ericoid mycorrhizal fungi (ERMFs) or dark septate endophytic fungi (DSEFs) on secondary metabolite production and growth promotion of Rhododendron pseudochrysanthum. The strains Rf9 (Cryptosporiopsis sp.) and Rf32 (Cryptosporiopsis sp.) were isolated from Rhododendron formosanum, whereas strains Rp7 (Phialocephala fortinii), Rp9 (Hyaloscyphaceae sp.), and Rp28 (Phialocephala fortinii) were isolated from R. pseudochrysanthum (R. morii). We studied their molecular relationships using phylogenetic analysis and divided these five strains into three groups (Cryptosporiopsis sp., Phialocephala fortinii, and Hyaloscyphaceae sp.). We found that strains Rf9 and Rf32 belonged to ERMFs, which form a hyphal complex with R. pseudochrysanthum, whereas strains Rp7, Rp9, and Rp28 belonged to DSEFs, which form microsclerotia on R. pseudochrysanthum. The endophytic fungi can promote the growth of R. pseudochrysanthum seedlings, and the total fresh weight of inoculated seedlings was higher than that of the control seedlings. In addition, the phytochemical profile showed that the methanolic extract of Rp7-inoculated seedlings had the highest content of rutin, hyperoside, quercitrin, and (2R,3S)-catechin among all inoculated seedlings. In conclusion, DSEFs and ERMFs promoted the growth response and secondary metabolite production of R. pseudochrysanthum seedlings.