Abstract
ABSTRACTBiological control is widely successful at controlling pests, but effective biocontrol agents are now more difficult to import from countries of origin due to more restrictive international trade laws (the Nagoya Protocol). 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, application of 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. 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, including how to implement this information into a selective 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 depend 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 analyses, transcriptomic and proteomic studies, and gene editing. Improving biocontrol practices includes 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.
Highlights
We review recent developments in the field of biological control that indicate that genetics-based solutions are key (Fig. 1)
We currently witness a revival of the idea to apply genetics to the improvement of biocontrol programs, by exploiting intraand interspecific variation (Lommen, de Jong, & Pannebakker, 2017; Kruitwagen et al, 2018), performing experimental evolution (Lirakis & Magalh~aes, 2019), adapting the microbiome for improved rearing methods (Ras et al, 2017; Koskinioti et al, 2020a, 2020b), and by population and field-monitoring of released agents (Roderick & Navajas, 2003; Stouthamer & Nunney, 2014; Coelho et al, 2016)
We present the current state and future prospects of using genetic and genomic methods towards that aim. We consider these methods from evolutionary and ecological contexts, that is how these methods can realistically operate in long-term breeding programs and in the field (Fig. 2). Because of their prevalence and economic importance, we focus on programs using arthropod biocontrol agents, these universal genetics principles overlap with other agents
Summary
One of the prime reasons preventing the uptake of genetic improvements of biocontrol agents is difficulty in deciding which traits to optimize. Candidate traits can be roughly subdivided into pest-suppression ability, adaptation to abiotic factors, reducing ecological risk, and improving mass production or storage [see Kruitwagen et al (2018) and Bielza et al (2020) for a comprehensive overview] For some traits, such as pest killrate, the direction of improvement is apparent as killing more pests is a primary determinant of biocontrol success (Stiling & Cornelissen, 2005). -predation simulations, two different optimized life-history strategies for the agents were found to result in higher potential economic returns, differing in plant-leaving decision and host handling time of the biocontrol agent, and in their respective fecundity, longevity, and dispersal ability. Such a general modelling framework can be parameterised for biocontrol. It is of key importance to uncover the genetic architecture of biocontrol traits if we aim efficiently to improve them
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