Quality Control of Baculoviral Bioinsecticide Production

Abstract

Agriculture is a discipline that has accompanied human beings since the beginning of civilization. The cultivation of different vegetables for centuries has allowed selecting varieties that far exceed the capabilities of many wild type plants originally used as a food source. That situation derived in the manipulation of natural ecosystems, transforming them into spaces where they can only grow and develop the desired species. In our world, plants are the staple diet of many organisms including invertebrates like Lepidoptera. During the larval stage, these insects can consume a large amount of leaf tissue causing serious damage to the plant. If we think that most vegetables have insect predators, agricultural crops can be transformed into an inviting habitat, allowing the development of these animals. In conclusion, all crops have pests that threaten their productivity. Given this scenario, many pest control strategies have been used by human beings to protect the health of their crops: treatment with chemical insecticides, development of transgenic plants and biological control applications (Christou et al, 2006; Gilligan, 2008). Baculovirus is a large family of insect pathogens that infect and kill different species of Lepidoptera, Hymenoptera and Diptera (Theilmann et al, 2005). In particular, many lepidopteron are pests in agriculture transforming these viruses in an important biocontrol tools for their natural hosts (Entwistle, 1998; Moscardi, 1999; Szewczyk et al, 2006). Baculoviruses have double-stranded circular DNA genomes of 80,000-180,000 bp, containing between 80 to 180 genes depending on the specie (van Oers & Vlak, 2007; Miele et al, 2011). In early stages of virus cycle, this pathogen is produced as Budded Viruses (BVs): the genome contained in a protein capsid (nucleocapsid), which is surrounded by a lipid membrane. In change, in the last phase of multiplication processes appear the Occluded Bodies (OBs): protein crystals (forming polyhedra or granules) containing nucleocapsids wrapped by a lipid membrane with a different composition (ODVs or Occluded Derived Viruses, with single or multiple nucleocapsids depending on the specie) (Rohrman, 2008). These two virus phenotypes have different biological properties; while OBs are specialists (infecting larvae by per os route with a narrow host range; responsible of primary infection in midgut cells), the BVs are generalists (infecting a wide range of different insect cells triggering their death; responsible for secondary infection). In the pest control strategies, baculoviruses (OBs) are introduced on the crops to infect and kill larvae through the production of an epizooty.