**3. An Overview of Fungal Diversity and Frequency**

Investigations on the mycobiota of plants frequently reported new taxa or new species distribution, and several fungi are still undiscovered or undetected. Numerous higher plants have developed a variety of resistance mechanisms to prevent fungal infections. However, the presence of weakly pathogenic fungi in healthy plant tissues highlights the evolutionary continuum between latent pathogens and symptomless endophytes [15]. Generally, all plants have symbiotic interactions with fungal endophytes which can influence host performance in terms of disease resistance [154–156], stress tolerance [157], and biomass accumulation [158]. Fungal endophytes may also change according

to plant tissues colonized [159], phenological growth stages, host genotypes [160], and geographical distribution areas [161].

In this review, a total of 428 endophytic species belonging to 122 fungal genera have been found in association with 13 plant genera (Table 1). The greatest level of fungal diversity was reported in in association with *Bauhinia* with 43 fungal genera and 94 fungal species, and *Cornus* with 44 fungal genera and 78 fungal species. The degree of fungal recovery from *Acacia* (29 genera, 51 species), *Albizia* (14 genera, 27 species), *Berberis* (17 genera, 29 species), *Caesalpinia* (19 genera, 42 species), *Cassia* (15 genera, 19 species), *Ligustrum* (20 genera, 29 species), and *Nerium* (21 genera, 37 species) was nearly half in comparison to the abundance noted in the genera *Bauhinia* and *Cornus*. Nonetheless, the lowest diversity showed for *Hamamelis*(4 species/genera), *Jasminus*(7 species, 1 genera), *Lonicera* (3 species/genera), and *Robinia* (6 species/genera) was also due to the lack of published research about fungal endophytes in these plant genera.

The literature evidenced that several fungal endophytes live in association with the investigated plants. The most representative genera in terms of abundance of isolated species were *Aspergillus* (40 spp.), *Penicillium* (30), *Fusarium* (29), *Colletotrichum* (27), *Alternaria* (14), and *Cladosporium* (14). These genera include ubiquitous and generalist fungi as well as several plant pathogens and saprobes [162–164].

It is worth noting the relative homogeneity in distribution of fungi such as *Colletotrichum*, *Fusarium,* and *Alternaria* among these plant genera. In fact, *Colletotrichum* was undetected only in *Lonicera* and *Robinia*, *Fusarium* in *Caesalpinia*, and *Hamamelis, Jasminus,* and *Alternaria* in *Cassia* and *Lonicera.* Although scarcely abundant, the fungal genus *Phyllosticta* was almost reported for all selected plants except for *Albizia*, *Jasminus*, *Robinia,* and *Hamamelis.* Other endophytic fungi were detected more occasionally. Future surveys may reveal the presence of additional fungal species also from less investigated plants, such as *Robinia*, *Jasminum,* and *Lonicera*.

The presence of pathogenic or saprotrophic fungi has already been discussed by several authors [165,166]. Table 1 shows that several of the listed fungi were apparently restricted to a single plant genus or at least exhibit some preference for a particular one. Some common and ubiquitous pathogens have been recovered in more than one plant host. This is the case of *F. oxysporum* (8 host plant species belonging to 7 different genera), *A. alternata*, *A. niger*, *C. gloeosporioides* (7 host plant species), *N. oryzae* (4 host plant species), *B. dothidea*, *C. globosum, C. acutatum* (3 host plant species), *A. ochraceus*, *A. pullulans*, and *C. truncatum* (3 host plant species).
