Biological Control Through Fungal Endophytes: Gaps In Knowledge Hindering Success

Background: The asymptomatic fungal endosymbionts of plants called the endophytes are universal in their occurrence. The occurrence of some entomopathogenic fungi which infect and kill insect pests of crops as endophytes provides an excellent opportunity for using these fungi in biocontrol. A few studies substantiate this novel approach of pest management; however, since this facet of endophyte research is nascent, enquiries answering basic questions on various aspects of endophyte biology are essential to successfully implement endophyte-mediated biocontrol. In a collaborative research, we addressed a few of these questions including (i) to what extent do fungal genera reported to have entomopathogenic species colonize non-crops as endophytes? (ii) can an endophyte from a non-crop source and vested with anti-insect property survive as an endophyte when introduced into a crop? (iii) how does an anti-insect endophyte in a crop affect an insect pest? and (iv) can endophytes be used for controlling weeds? The results of this study show that endophytes have enormous potential as biocontrol agents and reiterate the need for concerted efforts to obtain more basic information about endophyte biology before they can be used effectively for biocontrol. Methods: Non-entomopathogenic but anti-insect metabolites producing endophytes from plant and nonplant sources are shown to have potential biocontrol properties. Survival of an effective fungus from an alien source in a crop plant as an endophyte has been shown to be only for a limited period. Endophytes are shown to possess weedicidal activity. Results: Entomopathogenic fungal genera rarely colonize leaves of forest trees as foliar endophytes. Non-entomogenous endophytes produce anti-insect compounds affecting pests of crops thus having the potential as biocontrol agents. Such fungi isolated from non-plant sources can be inoculated into crops to function as endophytes, for brief periods. Insect pests avoid crops with anti-insect endophytes for oviposition and feeding. Some endophytes elaborate weedicidal compounds. Conclusion: Our basic study underscores the need to screen plants and non-plants of different habitats for entomopathogenic and anti-insect endosymbiotic fungi. Futhermore, it highlights the importance of screening endophytes for weedicidal compounds. We emphasise the need for focused studies for better understanding of the interaction between endophytes and their plant hosts and the biotic stressors of the host plants to enhance the success of using endophytes for biological control. Keywords: Biocontrol, pest management, entomopathogens, weedicides, endophytes, crop.