BERGERO, ROBERTA, SILVIA PEROTTO, MARIANGELA GIRLANDA, GABRIELE VIDANO & ANNA MARIA LUPPI.
Dipartimento di Biologia Vegetale and CSMT-CNR, Viale Mattioli 25, 10125 Torino, ITALY.
This work was undertaken to test the hypothesis that an ericaceous
and an ectomycorrhizal plant growing together could share common fungal root
associates. Root samples of Quercus ilex and Erica arborea were
collected in a mediterranean Q. ilex woodland (Italy) and surface sterilized
for the isolation of the fungal associates. Isolates were predominantly dark
and hyaline sterile mycelia. They were grouped in cultural morphotypes, some
of these including isolates obtained from both plants. Oidiodendron spp.
were also isolated from both plant species. In resynthesis trials of ericoid
mycorrhizas, sterile isolates assigned to three morphotypes were able to infect
hair roots of E. arborea and so recognized as ericoid symbionts. Such
a mycorrhizal ability was exhibited also by isolates obtained from roots of
Q. ilex, which in ITS/RFLP analysis resulted conspecific with isolates
obtained from E. arborea belonging to the same morphotype.
The spectrum of the shared root associates could be increased. There are strong
evidences that this ericaceous plant harbours a broader range of mycorrhizal
partners, whose recovery up to now has proven to be unsuccessful. Direct microscopic
observations showed that a variety of mycelia, differing in colour, hyphal diameter,
presence/absence of clamp connections were associated with Erica arborea.
A mycelium with clamp connections strongly colonized roots of E. arborea
by forming a loose sheath. Extensive coils within the epidermal cells were
observed. Ultrastructural analysis clearly confirmed their basidiomycetous nature.
This mycelium was never obtained from isolation trials. This proves the necessity
of overcoming limitations of the isolation technique by using molecular techniques.
In particular PCR amplifications of portions of the ribosomal genes from mycorrhizal
roots and subsequent sequence analysis will provide further data on the real
spectrum of ericoid endophytes. Some of these could be ectomycorrhizal in Q.
ilex and act as functional pathways for transport of nutrients between these
two plant species.