Morphological characteristics of rhizodermal colonization by Leohumicola species in an ericaceous host

Abstract

Lifecycle and temporal functionality of ericaceous fine roots can be affected by colonization dynamics of diverse root colonizing fungi. However, states of colonization are unknown for most of the root endophytes, which also obscures their lifestyles. To recognize characteristics of colonization of Leohumicola fungi, we investigated (1) the vitality of rhizodermal cells by using FUN-1 stain (vital staining) and (2) morphology of colonizing hyphae by N-acetylglucosamine-specific staining (DAB staining). All the twelve strains, identified as L. verrucosa, L. minima, and Leohumicola spp., colonized vital and non-vital rhizodermal cells of Vaccinium seedlings. We observed at least four different states of host cells encompassing coils. DAB staining visualized intracellular hyphae that resembled coils of typical ericoid mycorrhizal fungi. Heterogeneous staining states of coils were also observed in DAB staining. The variable states of Leohumicola coils can be comparable with ericoid mycorrhizal fungi, and indicate various developmental and functional stages of intracellular association.