Biological control of insect-pest and diseases by endophytes

Abstract

The natural and biological control of insect-pests and diseases affecting cultivated plants has gained much attention in the past decades as a way of reducing the use of pesticides in agriculture. Biocontrol has been frequently used in tropical countries, such as Brazil, and it is supported by the development of local basic and applied research. In this context, tropical endophytes have attracted special attention to develop their roles to control of pest insect and plant diseases. Endophytic symbiotic microorganisms are defined in different ways and a recent definition includes all of the culturable microorganisms that inhabit inner parts of plant tissues causing no harm to their hosts. They can be divided in two groups: those that do not generate external structures from the host and those able to develop external structures such as nodules of N 2 fixing bacteria and mycorrhizal fungi. Endophytes have important roles in the plant host protection, acting against predators and pathogens. They protect host plants against herbivores such as cattle and pest insect. They also may increase plant resistance to pathogens that produce antimicrobial agents and plant-growth hormones and have other effects countering biotic and abiotic stresses. Endophytic microorganisms were first studied in plants in temperate regions but more recently have been also studied in plants from tropical regions. In this chapter, we focus on examples of endophytic bacteria and fungi, especially those that may control pest insects and plant diseases by antagonistic effects, production of enzymes, or introduction of heterologous genes by recombinant DNA technology.