**3. Ecology and Occurrence**

As introduced above, endophytic fungi are polyphyletic groups of microorganisms, which asymptomatically colonize healthy tissues of different parts of living plants such as stems, leaves or roots. Their diversity is huge, and it has been estimated that every plant hosts several endophytic species, among which at least one shows host specificity [13,14]. Through the evolutionary processes, endophytic fungi have developed different symbiotic relationships with their host plants [3]. Furthermore, many species are reported to exhibit multiple ecological roles as both endophytes and pathogens. However, it is not clear whether the same genotypes can play both these roles with equal success. Understanding the mechanisms responsible for the conversion between so different outcomes of the ecological interaction represents one among many frontiers in endophyte biology [15,16]. One of the mechanisms developed by plants during the long-term co-evolution with microbial associates is the ability to produce antibiotic compounds. Simultaneously, many endophytes have developed an important transformative capacity and/or tolerance to these products which in a large part determines the colonization range of their hosts [17]. In turn, endophytes can influence growth and development of host plants, and enhance their resistance to biotic and abiotic stresses by releasing bioactive

metabolites [18], to such an extent that in natural habitats some plant species require to be supported by endophytic fungi for stress tolerance and survival [19].

The diversity of endophytic fungi associated with medicinal plants is largely affected by ecological or environmental factors. Particularly, temperature, humidity and soil nutritional conditions influence the quality and quantity of secondary metabolites synthesized by the hosts, which in turn affect the population structure of endophytic fungi. The species composition of endophyte communities also differs in organ and tissue specificities, as a result of their adaptation to different physiological conditions in hosts [3,20].

The analysis of the recent literature shows that species of sage (*Salvia* spp.) host diverse communities of fungal endophytes. As many as 64 different taxa belonging to 38 genera, with a clear prevalence of Ascomycetes, have been reported so far (Table 1). Most observations concern the species *Salvia miltiorrhiza* and *S. abrotanoides*, respectively, with 28 and 24 records. There is an evident correspondence between the *Salvia* species and the geographical area. In fact, all isolations concerning *S. miltiorrhiza* come from several provinces of China, while the available findings from *S. aegyptiaca* come from Egypt, and those referring to *S. abrotanoides* derive from an Iranian study and from the activity currently in progress at our laboratories. Despite the fact that isolations have been carried out from any plant organ (Figures 1 and 2), no indications concerning a specific association with roots or the aerial parts can be inferred. The access to biomolecular methods as a taxonomic tool has generally enabled to perform reliable identification at the species level, with the exception of a Chinese study concerning seeds of *S. miltiorrhiza*, where sorting was basically limited to the class level despite the wide variation observed [21]. The repeated findings in several species/locations mostly refer to strains provisionally identified at the genus level, particularly *Alternaria*, which seems to be of quite common occurrence on sages regardless to the plant part used for isolations. At the species level, there are only two cases with more than just one record—that is, *Chaetomium globosum* and *Didymella* (=*Phoma*) *glomerata*, both from *S. miltiorrhiza* at two different locations in China. However, the recovery of these species from both roots and leaves may represent a possible indication of a more regular association with this plant, which should be taken into consideration in further studies.


**Table 1.** Endophytic fungi reported from *Salvia* spp.


**Table 1.** *Cont.*

<sup>1</sup> Species are reported according to the latest accepted name, which might not be the same as the one used in the corresponding reference.

**Figure 1.** Isolation of endophytic fungi from leaf of *Salvia yangii* (original from work currently in progress at our laboratories).

**Figure 2.** Graphic representation of findings concerning endophytic fungi of *Salvia* spp. based on data reported in Table 1.
