4 Afra Khiralla, Rosella Spina, Sakina Yagi et al.
Host-specificity is the relationship in which a fungus is restricted to a
single host or a group of related species, but does not occur in other unrelated
plants in the same habitat (Holliday, 1998). Petrini (1991) used two different
terms, establishment specificity and expression specificity, to identify the
relationship. Establishment specificity was defined when an endophyte
colonizes only selected plant species, while expression specificity is
colonization of several hosts by a given fungus, but forming specific structures
(usually fruiting bodies) on a limited number of plant taxa. However, some
researchers found no or very little evidence of host-specificity in endophytes
(Umali et al., 1999, Andrew, 2000; Khiralla, 2015).
Added to that, some endophytes revealed tissue specificity. Bagchi and
Banerjee (2013) studied the tissue specificity symbiosis; they isolated
endophytic fungi from leaf, petiole and stem of Bauhinia vahlii. They found
that, the colonization frequency of endophytic fungi is much higher in petiole
(86.67%) in comparison to stem (77.33%) and leaf (70.67%). Whereas, some
researchers reported that endophytic fungal colonization is higher in leaf
segments rather than stem segments of some tropical medicinal plants
(Raviraja, 2005; Banerjee and Mahapatra, 2010).
Besides, some researchers stated other host relationship phenomenons
such as host-selectivity and host-preference. Host-selectivity is described
when one endophytic fungal species may form relationships with two related
plant species, but demonstrate a preference for one particular host (Cohen,
2006). The term host-preference, however, is more frequently used by
mycologists to indicate a common occurrence or uniqueness of the occurrence
of a fungus on a particular host. The differences in endophyte assemble from
different hosts might be related to the chemical differences of the host (Paulus
et al., 2006).
3. DOES CLIMATE EFFECTING FUNGAL
ENDOPHYTE COMMUNITIES?
Environmental factors, such as rainfall and atmospheric humidity might
influence the occurrence of some fungal endophyte species (Petrini, 1991;
Selvanathan et al., 2011). In the Sudan Khiralla et al., (2015; 2016) attempted
to analyze the diversity of the culturable fungal endophytes in 5 plant species
that are used in the traditional medicine. Only between three and six strains
were recovered from the leaves, stems and/or seeds per plant, however the