Next‐generation biological control: the need for integrating genetics and genomics

Abstract

Biological 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.

Jekyll or Hyde? The genome (and more) of Nesidiocoris tenuis, a zoophytophagous predatory bug that is both a biological control agent and a pest

“…Characteristics such as karyotype, sex chromosome system and presence or absence of telomeric repeats are currently unknown. A likely reason for this absence of genomic resources is that advances made in sequencing technology are often juxtaposed to the complexities of insect life cycles and difficulties in obtaining enough high quality genomic material due to size and exoskeleton (Richards and Murali, 2015; Leung et al ., 2020). In addition, current assembly tools have a hard time dealing with heterozygosity; therefore, a genome assembly is benefited by sequencing material of reduced genetic heterozygosity for a more contiguous assembly.…”

“…Generating the genomes of highly heterozygous, diploid and relatively small insects is tricky; researchers have to be prepared to balance their expectations and the available technology (Ellegren, 2014; Leung et al ., 2020). While a single diploid individual may yield enough material for an Illumina‐only library, assembly may be difficult due to large repeat regions that extend beyond the insert size of the library.…”

Use of zoophytophagous mirid bugs in horticultural crops: Current challenges and future perspectives

“…A renewed interest in genetic improvement of natural enemies has emerged to overcome some of the limitations that hinder further adoption of mirid bugs in biological control. 3,39,40 Mirid bugs possess certain biological traits which can be potentially improved. There is already evidence suggesting that there is variation which makes selection of distinct strains possible.…”

Learning can be detrimental for a parasitic wasp

“…Maladaptive learning has also been reported in parasitoid species used as biological control agents. When reared on alternative host species, artificial diets or artificial rearing units, parasitoids may partly loose their capacity to find and exploit the natural pest species [48,49]. For example, it was shown [50] that prior experience of Exeristes roborator (Hymenoptera: Ichneumonidae) when reared in an artificial arena significantly altered the behavioural response of parasitoid females to their host, the European pine shoot moth, Rhyacionia buoliana (Lepidoptera: Tortricidae), when released in forests.…”