Influence of thirteen different strains of ericoid endomycorrhizae on rooting and growth of micropropagated azalea mollis

In the wild, most of the Ericaceae are mycorrhized by typical ericoid endomycorrhizae thus overcoming the absence of root hairs and the difficulty of absorption of some nutrients in low pH soils. Many authors studied the relationship between root colonization and soil composition but only a few of them took in consideration the species of the fungi mycorrhizing the roots. Our previous works on Vaccinium pointed out the effects of different fungal strains on rooting and growth of in vitro produced plants. The aim of this research was to study the effect of the inoculum with different fungal strains on rooting, acclimatization and growth of the deciduous Azalea mollis cv. Glowing Embers (Rhododendron japonicum), micropropagated in vitro. Sterile microcuttings, planted on a sterilized turf substrate, were inoculated with Hymenoschiphus ericae, seven different strains of Oidiodendron maius, and some unidentified sterile mycelia, by superimposing the rooting medium on a pure fungal culture in agar. Rooting time and percentage was checked. Plant height and rosette diameter, leaf and shoot number of each plant were measured one year after transferring to ex vitro conditions. All tested strains were able to infect the roots of the azalea, but different effects were shown on microcutting rooting time and percentage. Oidiodendron strains were generally more effective than Hymenoschiphus on growth of established plantlets.