Endophytes inhibit plant pathogen growth and prevent or reduce disease development through the production of toxic alkaloids or by occupying the same ecological niche as the pathogen (Clay 1990). Studies found that three Bacillus strains and two Pseudomonas fluorescens strains decreased up to 60% of the disease symptoms caused by Pseudomonas syringae, a powdery mildew and angular leaf spot, and increased the fresh weight of inoculated melon plants compared with non-inoculated controls (Garcia-Gutierrez et al. 2012). In tomato plants, bio-control of Bacillus subtillis S499 was tested for antagonism against Fusarium spp. by treating the seeds with a formulated powder containing different concentrations of viable spores of B. subtillis S499, and results showed that all treatments significantly reduced disease severity up to 65-70% compared with control plants (non-inoculated seeds) (Nihorimbere et al. 2010).

Since endophytes have the ability to inhibit or prevent pathogen growth, they have been considered as biological control agents. In the interaction of Italian ryegrass (Lolium multiflorum Lam) with the fungal endophyte Neotyphodium, the ryegrass exhibited increased resistance to Trigonotylus caelestialium (Shiba et al. 2011). Additionally, the bird cherry oat-aphid (Rhopalosiphum padi), a notorious pest of forage and cereal grasses, showed a preference to non-infected plants of Alpine timothy (Pleum alpinum) over the plants infected with Neotyphodium spp. (Clement et al. 2011). Perennial ryegrass (L. perenne) plants colonized by N. lolii exhibited reduced aphid populations and in some cases the aphids exhibited reduced adult life­span and fecundity (Meister et al. 2006). Tall fescue plants inoculated with Neotyphodium coenophialum decreased the survival rate and feeding of the corn flea beetle, Chaetocnema pilucaria (Ball et al. 2011). Similar preferences were observed in Achnatherum inebrians (drunken horse grass) where Neotyphodium gansuense-infected plants decreased the preference of herbivores such as bird cherry-oat aphid, carmine spider mite (Tetranychus cinnabarius), grasshopper (Oedaleus decorus) and seed-harvesting ant (Messor aciculatus) due to high levels of ergine, ergonovine and ergoit alkaloids produced by the fungal endophyte (Zhang et al. 2011). Recently, endophytic bacteria isolated from root tissue of six plants growing in a tidal flat area of Korea showed antagonistic potential toward the pathogenic oomycete fungi Phytophtore capsici and Pythium ultimim, and some of them were able to degrade biopolymers, such as cellulose and p-1,3-glucan, which are major components of the cell wall of oomycetes (Bibi et al. 2012).

In switchgrass production, it was found that large-scale planting of switchgrass could be devastated by Puccinia emaculata Schwein, a rust fungus (Zhao B. http: //hayandforage. com/biofuels/rust-resistant — switchgrass-research-goal-0323). In the future, it may be possible to identify endophytes which produce antifungal compounds to help offset losses caused by the rust fungus.