Schaechter (2011) stated that endophytic fungi divided into two major groups due to variances in taxonomy, host range, colonization transmission patterns, tissue specificity and ecological function. Group one is the Clavicipitaceous endophytes (C-endophytes) which infect some grasses. Group two is the Nonclavicipitaceous endophytes (NCendophytes). While Rodriguez et al., (2009) stated another point of view of fungal endophytes classification, they classified them into four classes. Two major endophytic groups (Clavicipitaceous and Nonclavicipitaceous) based on phylogeny data and life history traits. However, they classified nonclavicipitaceous endophytes into three functional groups based on host colonization and transmission, in planta biodiversity and fitness benefits conferred to hosts.
1. Clavicipitaceous Endophytes (Class I)
The Clavicipitaceae is a family of fungi (Hypocreales; Ascomycota) including free living and symbiotic species associated with insects and fungi or grasses, rushes and sedges (Bancon and White, 2000). Many of its members produce alkaloids which are toxic to animals and humans
Mycelium of clavicipitaceous endophytes occurs in intercellular spaces of leaf sheaths, culms, and rhizomes, and may also be present, if sparsely, on the surface of leaf blades .
The effects of clavicipitaceous endophytes on host plant are listed below:
• Insects deterrence
Most clavicipitaceous endophytes improve resistance of hosts to insect feeding; The credit goes back to the production of toxins alkaloidic mycotoxins loline and peramine which are generally related with resistance to insects.
• Mammalian herbivores deterrence
Some clavicipitaceous endophytes are prevent feeding by mammalian herbivores, because they produced mycotoxins such like ergot and lolitrem alkaloids.
• Reduction of nematodes
Also some studies indicated that clavicipitaceous endophytes had antinematode activity; for example infection of tall fescus Festuca arundinacea with an endophytic fungus Acremonium coenophialum has been shown to reduce nematode population’s in field soils.
• Increase resistance of host disease
Also clavicipitaceous endophytes produced indole derivative compounds, a sesquiterpene, and a diacetamide from Epichloë festucae that inhibit the growth of other pathogenic fungi.
• Enhance the ecophysiology of host plants
Clavicipitaceous endophytes increase the ecophysiology of host plants and enable plants to counter abiotic stresses such as drought and metal contamination. Such as, Neothyphodium coenophialum infection leads to the development of extensive root systems that enable plants to better acquire soil moisture and absorb nutrients, resulting in drought avoidance and faster recovery from water stress. In some cases, endophytes motivate longer root hairs and enhance exudation of ‘phenolic-like compounds’ into the rhizosphere, resulting in more efficient absorption of soil phosphorus and enhanced aluminum tolerance by chelation .
2. Nonclavicipitaceous Endophytes (Class II)
Rodriguez et al., (2009), who showed that NC-endophytes represent three distinct functional groups. Class II endophytes include the hyperdiverse endophytic fungi associated with leaves of tropical trees as well as the highly diverse associates of above-ground tissues of nonvascular plants, seedless vascular plants, conifers, and woody and herbaceous angiosperms in biomes ranging from tropical forests to boreal and Arctic/Antarctic communities .Most fungal endophytes species belong to Ascomycetes, with a minority of Basidiomycetes. Fungal group ‘dark septate endophytes’ (DSE) are distinguished as a functional group based on the presence of darkly melanized septa.
The effects of these endophytes on host plant are listed below:
• Avoiding abiotic stress
One attribute that appears unique to Class II NC-endophytes is the ability of individual isolates to asymptomatically colonize and confer habitat-adapted, fitness benefits on genetically distant host species representing monocots and eudicots (Rodriguez et al., 2009). This phenomenon was discovered by comparing fitness benefits conferred by Class II endophytes in plants growing in geothermal soils Curvularia protuberate, coastal beaches Fusarium culmorum and agricultural fields Colletotrichum spp. (Redman et al., 2002; Márquez et al., 2007).
• Increase of biomass
Most of class II endophytes examined have increased host shoot and/or root biomass. Tudzynski and Sharon (2002) stated that this was a result of the induction of plant hormones by the host or biosynthesis of plant hormones by the fungi.
• Protection from fungal pathogens
Many endophytes of class II protect hosts to some extent against fungal pathogens (Danielsen and Jensen, 1999; Narisawa et al., 2002; Campanile et al., 2007) by different strategies like production of secondary metabolites (Schulz et al., 1999). Few studies revealed interactions with host defenses; fungal parasitism (Samuels et al., 2000); induction of systemic resistance (Vu et al., 2006); or competition with endophytes for resources or niche space