Isolation, storage, and use of ericoid mycorrhizal fungi for improved acclimatization and subsequent growth of micropropagated Pieris floribunda

Cleared and stained hair roots of wild-collected plants of Pieris floribunda, growing in a naturally occurring stand in the Blue Ridge Mountains of North Carolina, exhibited typical ericoid mycorrhizae. Two fungi (B3 and C1) were isolated from mycorrhizae and grown in axenic culture on an artificial medium. Only C1 established mycorrhizae with roots of seedlings of P. floribunda. Based on colony morphology and sporulation characteristics in axenic culture, isolate C1 was identified tentatively as a member of the genus, Oidiodendron.; Lyophilization was effective in maintaining viability of select, nonsporulating isolates of Hymenoscyphus ericae and sporulating isolates of Oidiodendron spp. These fungi remained viable up to 1 year following lyophilization when stored at {dollar}rm {lcub}-{rcub}80spcirc C{dollar} under normal atmospheric gases. Similarly, two isolates of H. ericae cultured on a peat-based medium also survived lyophilization and subsequent storage. Storage at {dollar}rm 4spcirc C{dollar} or {dollar}rm {lcub}-{rcub}20spcirc C{dollar} resulted in the greatest long-term viability. Room-temperature storage {dollar}rm (23spcirc C){dollar} resulted in rapid loss of viability of one of two isolates of H. ericae. Both isolates of H. ericae formed typical ericoid mycorrhizae with roots of seedlings of P. floribunda following rehydration and revival in vitro. Mycorrhizal seedlings exhibited increased growth over noninoculated controls, indicating the fungi retained both infective and functional characteristics of mycorrhizal fungi throughout lyophilization and long-term storage.; Oidiodendron griseum, O. maius, and another Oidiodendron sp. caused different severities of shoot necrosis on microshoots of P. floribunda. Inoculation of micropropagated plantlets with isolates of H. ericae benefitted initial shoot and root development on agar-solidified Woody Plant Medium supplemented with sucrose and covered by a layer of 1 peat: 1 vermiculite (v/v).; Acclimatization of plantlets of P. floribunda to greenhouse conditions following in vitro inoculation with isolates of H. ericae (HE or DA) resulted in improved survival (42%) over noninoculated plantlets (16%). Microshoots of P. floribunda inoculated with isolates of H. ericae produced significantly greater shoot growth than noninoculated microshoots after in vitro growth for 1 month. However, no benefits were realized from mycorrhizal inoculation of plantlets after 3 months growth in a greenhouse.