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Invasive species are increasingly affecting agriculture, food, fisheries, and forestry resources throughout the world. As a result of global trade, invasive species are often introduced into new environments where they become established and cause harm to human health, agriculture, and the environment. Prevention of new introductions is a high priority for addressing the harm caused by invasive species, but unfortunately efforts to prevent new introductions do not address the economic harm that is presently manifested where invasive species have already become established. Genetic biocontrol can be defined as the release of organisms with genetic methods designed to disrupt the reproduction of invasive populations. While these methods offer the potential to control or even eradicate invasive species, there is a need to ensure that genetic biocontrol methods can be deployed in a way that minimizes potential harm to the environment. This review provides an overview of the state of genetic biocontrol, focusing on several approaches that were the subject of presentations at the Genetic Biocontrol for Invasive Species Workshop in Tarragona, Spain, March 31st, 2019, a workshop sponsored by the OECD's Co-operative Research Program on Biological Resource Management for Sustainable Agricultural Systems. The review considers four different approaches to genetic biocontrol for invasive species; sterile-release, YY Males, Trojan Female Technique, and gene drive. The different approaches will be compared with respect to the efficiency each affords as a genetic biocontrol tool, the practical utility and cost/benefits associated with implementation of the approach, and the regulatory considerations that will need to be addressed for each. The opinions expressed and arguments employed in this publication are the sole responsibility of the authors and do not necessarily reflect those of the OECD or of the governments of its Member countries. The opinions expressed and arguments employed in this publication are the sole responsibility of the authors and do not necessarily reflect those of the OECD or of the governments of its Member countries. This article resulted from the Genetic Biocontrol for Invasive Species Workshop, which was sponsored by the OECD Co-operative Research Programme: Biological Resource Management for Sustainable Agricultural Systems, whose financial support made it possible for most of the authors to participate in the Workshop. Roberts, A (corresponding author), ILSI Res Fdn, Washington, DC 20005 USA. aroberts@foodsystems.org

Frosty pod rot (FPR) of Theobroma cacao (cacao) is caused by the hemibiotrophic fungus Moniliophthora roreri. Cacao clones tolerant to FPR are being planted throughout Central America. To determine whether M. roreri shows a differential molecular response during successful infections of tolerant clones, we collected field-infected pods at all stages of symptomatology for two highly susceptible clones (Pound-7 and CATIE-1000) and three tolerant clones (UF-273, CATIE-R7 and CATIE-R4). Metabolite analysis was carried out on clones Pound-7, CATIE-1000, CATIE-R7 and CATIE-R4. As FPR progressed, the concentrations of sugars in pods dropped, whereas the levels of trehalose and mannitol increased. Associations between symptoms and fungal loads and some organic and amino acid concentrations varied depending on the clone. RNA-Seq analysis identified 873 M. roreri genes that were differentially expressed between clones, with the primary difference being whether the clone was susceptible or tolerant. Genes encoding transcription factors, heat shock proteins, transporters, enzymes modifying membranes or cell walls and metabolic enzymes, such as malate synthase and alternative oxidase, were differentially expressed. The differential expression between clones of 43 M. roreri genes was validated by real-time quantitative reverse transcription polymerase chain reaction. The expression profiles of some genes were similar in susceptible and tolerant clones (other than CATIE-R4) and varied with the biotrophic/necrotropic shift. Moniliophthora roreri genes associated with stress metabolism and responses to heat shock and anoxia were induced early in tolerant clones, their expression profiles resembling that of the necrotrophic phase. Moniliophthora roreri stress response genes, induced during the infection of tolerant clones, may benefit the fungus in overcoming cacao defense mechanisms.

Metadata only record The aim of this study was to determine whether endophytic Bacillus cereus isolates from agronomic crops possessed genes for the nonhaemolytic enterotoxin (Nhe) and haemolysin BL (HBL) and, therefore, have the potential to cause diarrheal illness in humans. LTRA-7 (Pathways to CAPS in the Andes)

Endophytic Trichoderma isolates collected in tropical environments were evaluated for biocontrol activity against Phytophthora capsici in hot pepper (Capsicum annuum). Six isolates were tested for parasitic and antimicrobial activity against P. capsici and for endophytic and induced resistance capabilities in pepper. Isolates DIS 70a, DIS 219b, and DIS 376f were P. capsici parasites, while DIS 70a, DIS 259j, DIS 320c, and DIS 376f metabolites inhibited P. capsici. All six isolates colonized roots but were inefficient stem colonizers. DIS 259j, DIS 320c, and DIS 376f induced defense-related expressed sequence tags (EST) in 32-day-old peppers. DIS 70a, DIS 259j, and DIS 376f delayed disease development. Initial colonization of roots by DIS 259j or DIS 376f induced EST with potential to impact Trichoderma endophytic colonization and disease development, including multiple lipid transferase protein (LTP)-like family members. The timing and intensity of induction varied between isolates. Expression of CaLTP-N, encoding a LTP-like protein in pepper, in N. benthamiana leaves reduced disease development in response to P. nicotianae inoculation, suggesting LTP are functional components of resistance induced by Trichoderma species. Trichoderma isolates were endophytic on pepper roots in which, depending on the isolate, they delayed disease development by P. capsici and induced strong and divergent defense reactions.

This presentation details work done in SANREM CRSP phase III on biological control of fungal and other diseases in cacao. LTRA-7 (Pathways to CAPS in the Andes)

"Interest in ecologically-based management of cacao diseases has lead to research on biocontrol. Sixty-nine endophytic Bacillus spp. were isolated from cacao trees escaping disease near Quevedo, Ecuador and screened as potential biological control agents. Four elite Bacillus spp. are currently being field evaluated to determine their ability to suppress witches' broom disease, caused by Moniliophthora perniciosa. Research was conducted to determine how applications of biocontrol agents impacts diversity and abundance of native microbial communities. Since most endophytes are likely neutral in terms of plant health, it is hypothesized that application of beneficial bacteria will displace neutral endophytes to positively impact overall plant health. Each isolate was applied to runoff at log 8.0 CFU/ml with 0.20% Silwet L-77 adjuvant to 4 branches each of 3 replicate nacional trees per treatment. Controls consisted of application of adjuvant alone. Three months after both the application and reapplication of the bacteria, leaf discs were excised from 2 sprayed leaves per branch. Leaf discs from one tree were combined and placed in RNALater for preservation during shipment. Genomic DNA was extracted from the sample and Automated Ribosomal Intergenic Spacer Analysis (ARISA) was utilized to determine ecological shifts in both bacterial and fungal communities. Data will be presented on effects of application of these biocontrol agents on native microbial communities." (Abstract from meeting website: http://www.apsnet.org/meetings/2009/abstracts/a09ma495.htm) LTRA-3 (Watershed-based NRM for Small-scale Agriculture)

Presentation on biological suppression of cacao diseases from Ph.D. dissertation. LTRA-3 (Watershed-based NRM for Small-scale Agriculture)

Powerpoint presentation on cacao disease supression research in Ecuador LTRA-3 (Watershed-based NRM for Small-scale Agriculture)

This Penn State study examines the effectiveness of endophytic bacteria on cacoa trees as a biocontrol agent for witches' broom. The study involved field trials on seedlings with various levels of susceptibility. The application of bacteria was found to be most effective for tolerant genotype seedlings, but was not statistically significant for highly resistant strains.

Metadata only record Technical paper on biocontrol of cacao disease LTRA-3 (Watershed-based NRM for Small-scale Agriculture)