Table 1.
Effects of fungal endophytes on their colonized host plants and the primary pests.
| S/N | Fungal endophyte effects | Reference |
|---|---|---|
| 1 | Fungal endophytes induce systemic resistance in the colonized plants. They could also be transferred vertically from parent plants to their offspring, hence providing same resistance for the next generation. | Saikkonen et al., 2002; Griffin et al., 2006; Ownley et al., 2008b |
| 2 | Fungal endophytes protect host plants against plant pathogens. This has been reported in B. bassiana and Lecanicillium longisporum. | Kim et al., 2007, 2008, 2010; Ownley et al., 2008b; Jaber and Salem, 2014; Jaber, 2015; Puri et al., 2016 |
| 3 | Fungal endophytes have also been found to induce a reduction in insects feeding on endophytic colonized plants. | Knoch et al., 1993 |
| 4 | Endophytic fungi alter the nutritional level of the colonized plant and utilize this in the production of secondary metabolites. Certain chemical defenses previously reported to have been mediated by the plant have recently been proven to be induced by endophytic fungi. | Rowan et al., 1986 |
| 5 | Fungal endophytes improve tolerance of colonized plants to biotic stress such as root herbivory by plant parasitic nematodes. | Sikora et al., 2007, 2008; Cosme et al., 2016 |
| 6 | Fungal endophytes assist the colonized host plants in providing protection against insect herbivores. They cause retardation of insect growth, developmental rate and adult survival rate. | Saikkonen et al., 2004; Arnold and Lewis, 2005; Lacey and Neven, 2006; Jallow et al., 2008; Kim et al., 2008, 2010; Muvea et al., 2014; Resquín-Romero et al., 2016; Jaber and Araj, 2017; Rondot and Reineke, 2018; Sánchez-Rodríguez et al., 2018 |
| 7 | After successful colonization of the plant, certain fungal endophytes prevent colonization of the same plant by other foreign parasitic organisms. They produce chemicals that inhibit the growth of other pathogenic organisms and competitors. | Moy et al., 2000; Martinuz et al., 2012 |
| 8 | Fungal endophytes cause deterrence, the potentials of repelling insects from feeding on colonized plants has been ascribed to fungal endophytes. The mechanism for deterrence has been linked to the changes in the chemical composition of the endophytically colonized plants. | Latch et al., 1985; Tanada and Kaya, 1993; Daisy et al., 2002; McGee, 2002 |
| 9 | Fungi promote nutrients uptake in their colonized plants. The increase in phosphorus and nitrogen uptake has been reported | Behie et al., 2012; Behie and Bidochka, 2014 |
| 10 | They improve the plant’s tolerance to abiotic stresses, such as salt, drought or heat stresses. Improvement in overall plant hardiness has also been reported as endophytic fungi effects. | Márquez et al., 2007; Hamilton and Bauerle, 2012; Junker et al., 2012; Khan et al., 2012 |
| 11 | Fungal endophytes improve crop yield, plant growth, cell division and development. Improvement in crop yield and fresh weight of common bean and corn plants treated with M. anisopliae, B. bassiana and H. lixii has been reported. Also, B. bassiana and M. brunneum improved several growth parameters in sweet pepper (C. annum) and V. faba. | Kabaluk and Ericsson, 2007; Elena et al., 2011; Behie et al., 2012; Sasan and Bidochka, 2012; Behie and Bidochka, 2014; Liao et al., 2014; Lopez and Sword, 2015; Gathage et al., 2016; Jaber and Enkerli, 2016; Jaber and Araj, 2017; Jaber and Enkerli, 2017 |
| 12 | Oviposition rate is reduced; fungal endophytes make plant herbivores sterile and less productive, through changes in the chemical composition or profiles of the host plants that deter oviposition of adult insects. | Schmidt and Osborn, 1993 |
| 13 | Fungal endophytes also serve as reservoirs of novel bioactive compounds. They produce metabolites, antibiotics, bioactive volatile compounds (such as ammonia, lipids, alkyl pyrones, hydrogen cyanide, alcohols, ketones and esters). | Clark et al., 1989; Bills et al., 1992; Calhoun et al., 1992; White et al., 2003; Schardl et al., 2013 |
| 14 | Endophytic fungi indirectly enhance seed dispersal by ants | Knoch et al., 1993 |
| 15 | Aside from insects’ deterrence, there are also reports of fungal endophytes ability to deter vertebrate herbivores such as birds, rabbits and deer from feeding on fungal colonized plants. | Lekberg and Koide, 2005 |
| 16 | Fungal endophytes (in the case of mycorrhizae) distribute nutrients within the surrounding plants and other mycorrhizae. | Franklin et al., 2014 |
| Some detrimental effects on host plants and natural enemies | ||
| 17 | Fungal endophytes build up the host defense system at the detriment of the reproductive potential. Certain fungal endophytes were found to render grasses partially sterile at the expense of their fungal reproductive structures. | Clay et al., 1989 |
| 18 | In some cases, fungal endophytes when occurring in plant might increase transpiration rate in the leaves. | White et al., 1993 |
| 19 | Some endo-mycorrhizae may increase herbivore damage in plants by making their host plants more susceptible to the insect pests. | Mueller et al., 2005 |
| 20 | Fungal endophytes may indirectly protect insect pests against their natural enemies, by producing alkaloids such as ergovaline, loline, etc. that reduce the developmental rate and survival of natural enemies. Certain endophytic fungi-induced toxins mediate reduced susceptibility of insects to their natural enemies such as parasitoids and entomopathogenic nematodes. | Bultman et al., 1997; Omacini et al., 2001; Kunkel and Grewal, 2003; Kunkel et al., 2004 |