Review Applying molecular-based approaches to classical biological control of weeds John F. Gaskin a,⇑ , Marie-Claude Bon b , Matthew J.W. Cock c , Massimo Cristofaro d , Alessio De Biase e , Rose De Clerck-Floate f , Carol A. Ellison g , Hariet L. Hinz c , Ruth A. Hufbauer h , Mic H. Julien i , René Sforza b a USDA Agricultural Research Service, 1500 N. Central Avenue, Sidney, MT 59270, USA b European Biological Control Laboratories, USDA Agricultural Research Service, Campus International de Baillarguet, 34980 Montferrier le Lez, France c CABI Europe – Switzerland, Rue des Grillons 1, CH-2800 Delémont, Switzerland d ENEA Casaccia, UTAGRI-ECO (BBCA), Via Anguillarese 301, Rome 00123, Italy e Department of Biology and Biotechnologies ‘‘Charles Darwin’’, University of Rome ‘‘La Sapienza’’, Viale dell’Università 32, I-00185 Rome, Italy f Agriculture and Agri-Food Canada, Lethbridge Research Centre, 5403 1 Ave S, Lethbridge, Alberta, Canada T1J 4B1 g CABI Europe – UK, Bakeham Lane, Egham, Surrey, TW209TY, United Kingdom h Department of Bioagricultural Sciences and Pest Management and Graduate Degree Program in Ecology, Colorado State University, Fort Collins, CO 80523, USA i CSIRO Ecosystem Sciences, Ecosciences Precinct, 41 Boggo Road, Dutton Park, Qld 4102, Australia article info Article history: Received 14 October 2010 Accepted 30 March 2011 Available online 5 April 2011 Keywords: Biological control Weeds Invasion Molecular Arthropods Microorganisms Fungi abstract The use of molecular techniques is rapidly growing as the tools have become more diverse and powerful, more widely available, and easier to implement. Molecular analyses are able to elucidate information about target weeds that is critical to improving control success, such as taxonomic clarification, evidence of hybridization and cryptic species, better development of test plant lists, population structure and ori- gin of invasions. Similarly, molecular approaches can improve our knowledge of biological control agents, providing taxonomic clarity, identification of immature arthropods and fungal pathogens, and descrip- tion of genetic variability in agents. Molecular tools also allow easier identification of host associations and provide a tool for post-release evaluation and tracking of agents. This review provides an overview of how to use molecular approaches in biological control of weeds, with the aim of assisting the adoption and facilitating fruitful collaboration between scientists studying the biology and ecology of agents and their targets and those with skills using molecular approaches. We describe the current molecular tech- niques relevant to classical biological control of weeds, instruct how to collect field materials for molec- ular analyses, and give recent examples of the use of molecular methods in biological control of weeds, with comments on the most appropriate methods for analysis of molecular data. Published by Elsevier Inc. 1. Introduction A critical goal of scientists engaged in biological control of weeds is to reduce the risk of non-target and indirect effects by releasing fewer, more host-specific, and more effective agents (Strong and Pemberton, 2001; Louda et al., 2003; Balciunas, 2004). Molecular-based approaches have much to offer in attaining this goal (Briese, 2005; Goolsby et al., 2006), providing both pre- and post-release information that is simply not available, or not readily available, using other means. Molecular data can clarify taxonomy and evolutionary relationships, uncover evidence of clo- sely related species that cannot be morphologically distinguished (cryptic species) and hybridization events, elucidate methods of reproduction and complex life cycles of pathogens, determine pop- ulation structure and origins of target weeds and agents, and identify arthropods at immature life stages which cannot other- wise be distinguished from similar species. Molecular methods, like biological control, have their limita- tions. Molecular genetic data are most useful when good taxo- nomic, morphological, ecological, historical and demographic information are available to complement them and provide the context for understanding results. Molecular methods can also be costly and time consuming, and at times, gaps in biological control programs can be addressed without resorting to them. But DNA based molecular markers have the advantage that they are not nor- mally influenced by environmental stimuli or plasticity, unlike most morphological and other phenotypic data. In addition, the variety of molecular methods is continually expanding so that some questions can now be more easily answered, and improve- ments in protocols and equipment are making these tools cheaper and more accessible to those that do not specialize in their use. There have been previous reviews of the use of molecular ap- proaches for biological control and invasions (e.g. Nissen et al., 1995; Unruh and Wooley, 1999; Antonini et al., 2008; Rector, 1049-9644/$ - see front matter Published by Elsevier Inc. doi:10.1016/j.biocontrol.2011.03.015 ⇑ Corresponding author. Fax: +1 406 433 5038. E-mail address: john.gaskin@ars.usda.gov (J.F. Gaskin). Biological Control 58 (2011) 1–21 Contents lists available at ScienceDirect Biological Control journal homepage: www.elsevier.com/locate/ybcon