Inoculation of Rhododendron cv. Belle-Heller with two strains of Phialocephala fortinii in two different substrates

The growth response of an ornamental Rhododendron hybrid to the inoculation with Phialocephala fortinii was studied in two pot experiments in order to decide about the effectiveness of the inoculation of young rhododendron microplants. Two different substrates were used in both experiments, either sterilized or non-sterilized: a horticultural substrate and a soil collected from a field site with dominant ericoid vegetation. Two fungal isolates were used for an inoculation: P.fortinii strain P (UAMH 8433) and P.fortinii strain F, a dark septate endophyte (DSE) previously isolated from naturally-infected roots of Vaccinium myrtillus. Both Phialocephala strains successfully colonized the roots of the host plants forming typical DSE ( pseudomycorrhizal) colonization pattern including the formation of intracellular microsclerotia. However, pseudomycorrhizal colonization did not affect the growth parameters of the host rhododendrons. The results from both experiments indicate a neutral effect of the inoculation with DSE fungi on the growth of Rhododendron cv. Belle-Heller.