Next Generation Biological Control: The Need for Integrating Genetics and Evolution

Abstract

Biological control is widely successful for controlling pests, but effective biocontrol agents are now more difficult to obtain due to more restrictive international trade laws. Coupled with increasing demand, the efficacy of existing and new biocontrol agents needs to be improved with genetic and genomic approaches. Although they have been underutilised in the past, applying genetic and genomic techniques is becoming more feasible from both technological and economic perspectives. We review current methods and provide a framework for using them, incorporating evolutionary and ecological principles. First, it is necessary to identify which biocontrol trait to select and in what direction. Next, the genes or markers linked to these traits need be determined to better target their selection, followed by how to implement this information into a breeding program. Choosing a trait can be assisted by modelling to account for the proper agro-ecological context, and by knowing which traits have sufficiently high heritability values. We provide guidelines for designing genomic strategies in biocontrol programs, which depends on the organism, budget, and desired objective. Genomic approaches start with genome sequencing and assembly. We provide a guide for deciding the most successful sequencing strategy for biocontrol agents. Gene discovery involves quantitative trait loci (QTL) analyses, transcriptomic and proteomic studies, and gene editing. Improving biocontrol practices include marker-assisted selection, genomic selection and microbiome manipulation of biocontrol agents, and monitoring for genetic variation during rearing and post-release. We conclude by identifying the most promising applications of genetic and genomic methods to improve biological control efficacy.

Genetic Variation of Traits in Natural Enemies Relevant for Biological Control: A Systematic Review

“…In terms of number of observations, the next group of traits are those 'useful in improving mass rearing conditions', which would include life history traits such as sex ratio. These are potentially two of the more important classes within the classification for biological control application, indicating that the traits outlined in Leung et al are in line with the current trends in biological control research (Leung et al, 2019). It is also important to note that certain traits could fit into several of the biological control trait classifications, whereas the Mousseau and Roff classifications are clear-cut.…”

“…An important goal of our analysis is the categorization of traits according to fitness component, or importance to biological control research. Given the variety of traits being measured, both in nomenclature and formulation, categories were assigned and pooled by observation count in two ways: the Mousseau and Roff assessment based on biological function used in their review of the heritability of fitness components, and the Leung et al 2019 assessment based on biological control application (Mousseau and Roff 1987;Leung et al 2019). The outcome of the Mousseau and Roff assessment indicates that the majority of the 302 observations were of life history traits (53%), followed by behavior (21%), morphology (19%), and physiology (7%; Figure 5).…”

“…The second assessment method, based on biological control application (Leung et al 2019), allowed for multiple classifications per observation (364 total). As shown in Figure 6, the majority of the traits measured were related to pest suppression ability (53%), followed by improving mass rearing conditions (23%).…”

“…Due to knowledge gained on the risks of releasing non-native species, along with stricter regulations on the import and export of species (such as the Nagoya Protocol on Access and Benefit Sharing, 2010), this practice has become less desirable (CBD Secretariat, 2011;Lommen et al, 2017). These recent developments in combination with an expansion of pest ranges due to global warming and the anthropogenic movement of produce across the globe, make it more important than ever to improve the efficacy of those native natural enemies that are already at our disposal (Leung et al, 2019;Lommen et al, 2017).…”

“…With the increased interest in the role of experimental evolution and artificial selection in the improvement of biological control (Kruitwagen et al, 2018;Leung et al, 2019;Lirakis and Magalhães, 2019;Lommen et al, 2017;Routray et al, 2016), it is necessary to determine what has already been assessed with regards to genetic variation and heritable traits of BCAs, and where there are gaps in our knowledge.…”