Epsilon Archive for Student Projects

Abstract

Fungal endophytes are a taxonomically and ecologically heterogeneous group of ubiquitous
intercellular fungi that live part of their life within the tissues of the plants without causing
apparent harm to the host. They may contribute to the stress tolerance and resistance of the
plants, and endophytes may also be involved in decomposition processes. Thus, these fungi
are an interesting part of biodiversity e.g. in forest ecosystems. Little is still known about the
temporal and spatial patterns in endophyte community structures in trees. Moreover, while it
is known that endophytes spread to trees from the environment (horizontally) it is not clear at
which scales their spreading occurs, and if e.g. neighbouring vegetation determines endophyte
communities in trees. In addition, it is not known if the general vitality of the trees affects the
frequency and diversity of endophyte infections in trees. Using culture-dependent method
(isolations), endophyte communities were compared in young pedunculate oak (Quercus
robur L.) trees that were surrounded by herbs and shrubs in different combinations and that
showed different vitality status. The isolations were done from current and previous year’s
twigs (xylem and bark) in early and late summer to study the temporal and within-tree spatial
patterns. A total of 384 samples were plated with bark and xylem pieces. Altogether 172 of
them produced a total number of 285 isolates, which could be grouped in 22 morphological
groups (morphotypes). The colonisation and isolation rate values showed the succession of
endophyte communities during the season and inside the twigs but there were no significant
effects of tree vitality on these rates. However, in June the declining trees had higher
morphotype evenness, indicating that declining trees were compromised in their ability to
defend themselves against fungal infections, which may have reduced the competition
between the different invading fungi. The Jaccard’s similarity index and Shannon’s diversity
index showed that there was no clear pattern of infection from the closest surrounding
vegetation, suggesting that the spreading of these fungi occurs at a larger scale.