Scientific Methods Workshop: Ecological and Agronomic Consequences of Gene Flow from Transgenic Crops to Wild Relatives Meeting Proceedings The University Plaza Hotel and Conference Center The Ohio State University Columbus, OH March 5th and 6th, 2002 Steering Committee: Dr. Allison Snow (Chair and Co-PI), Ohio State University Dr. Carol Mallory-Smith (Co-PI), Oregon State University Dr. Norman Ellstrand, University of California at Riverside Dr. Jodie Holt, University of California at Riverside Dr. Hector Quemada, Crop Technology Consulting, Inc., Kalamazoo, MI Logistical Coordinator: Dr. Lawrence Spencer, Ohio State University Page Intentionally Blank Table of Contents Speakers/Titles Page No. Workshop Steering Committee 3 Introduction Bert Abbott, Clemson University 6 “Molecular genetic assessment of the risk of gene escape in strawberry, a model perennial study crop” Paul Arriola, Elmhurst College 25 “Gene flow and hybrid fitness in the Sorghum bicolor – Sorghum halepense complex” Lesley Blancas, University of California, Riverside 31 “Patterns of genetic diversity in sympatric and allopatric populations of maize and its wild relative teosinte in Mexico: evidence for hybridization” Norm Ellstrand, University of California, Riverside 39 “Gene flow from transgenic crops to wild relatives: what have we learned, what do we know, what do we need to know?” Jodie Holt, University of California, Riverside (Plenary Speaker) 47 “Prevalence and management of herbicide-resistant weeds” Diana Pilson, University of Nebraska 58 “Fitness and population effects of gene flow from transgenic sunflower to wild Helianthus annuus” Hector Quemada, University of Western Michigan 71 “Case Study: Gene flow from commercial transgenic Cucurbita pepo to ‘free-living’ C. pepo populations” Christiane Saeglitz, Aachen University of Technology 78 “Monitoring the environmental consequences of gene flow from transgenic sugar beet” Gene Flow Workshop, The Ohio State University, March 5 and 6, 2002 Proceedings Cynthia Sagers, University of Arkansas 94 “Ecological Risk Assessment for the Release of Transgenic Rice in Southeastern Arkansas” Neal Stewart, University of North Carolina, Greensboro 106 “Gene flow and its consequences: Brassica napus (canola, oilseed rape) to wild relatives” Steve Strauss, Oregon State University 113 “Gene flow in forest trees: From empirical estimates to transgenic risk assessment” James L. White, U.S. Department of Agriculture 134 “U.S. Regulatory Oversight for the Safe Development and Commercialization of Plant Biotechnology” Joseph Wipff, Pure Seed Testing, Inc. 143 “Gene flow in turf and forage grasses (Poaceae)” Chris Wozniak, U.S. Environmental Protection Agency 162 “Gene flow assessment for plant-incorporated protectants by the Biopesticide and Pollution Prevention Division, U.S. EPA” Robert Zemetra, University of Idaho 178 “The evolution of a biological risk program: Gene flow between wheat (Triticum aestivum L.) and jointed goatgrass (Aegilops cylindrica Host)” Gene Flow Workshop, The Ohio State University, March 5 and 6, 2002 Proceedings Page 3 SUMMARY Gene flow from transgenic plants to wild relatives is one of the major research areas targeted by USDA’s Biotechnology Risk Assessment Research Grants Program (BRARGP). We received funds for a two-day workshop that brought together researchers who study the prevalence and consequences of gene flow from transgenic crops to weeds and other wild relatives. On the first day, speakers discussed the general context for gene flow research, the information needs of USDA-APHIS, EPA, and the biotechnology industry, and case studies of specific crop-wild complexes, including cucurbits, brassicas, sunflower, sorghum, rice, wheat, maize, strawberry, poplar, and turfgrasses. Written summaries of these talks are included below. On the second day, breakout groups discussed the advantages and disadvantages of various approaches for studying the occurrence of gene flow and various effects of gene flow (fitness effects of transgenes in wild relatives, effects on population dynamics, indirect community effects, and effects on the genetic diversity of wild relatives). The crops, wild relatives, and regulatory issues we discussed focused on the USA, but much of the workshop was also relevant to similar situations in other countries. Proceedings and abstracts from the workshop are available for download from the workshop website (www.biosci.ohio-state.edu/~lspencer/gene_flow.htm). Bridging the fields weed science and plant ecology, we discussed the most appropriate and rigorous empirical methods available for studying questions related to gene flow from transgenic crops to weedy and wild relatives. BACKGROUND AND GOALS Gene flow between crops and free-living, noncultivated plants is often considered to be an undesirable consequence of adopting transgenic crops (e.g., NRC 1989, NRC 2000). This process occurs when pollen moves from a crop to its wild or feral relative – or vice versa – and genes from their offspring spread further via the dispersal of pollen and seeds. In addition, some crops, such as oats, radish, and oilseed rape, can proliferate as feral weeds. Although crops and weeds have exchanged genes for centuries, transgenes can confer novel, fitness- related traits that were not available previously, and the same transgenes can be introduced into many different crops, increasing the potential for their escape (e.g., resistance to the herbicide glyphosate). A fundamental question, then, is what impacts could single or multiple transgenes have on the abundance and distribution of wild relatives? From a regulatory perspective, it is useful to compare the effects of transgenes to effects of nontransgenic crop genes that spread to wild and/or weedy populations, keeping in mind that certain traits developed through the introduction of transgenes (e.g. herbicide tolerance, herbivore and pathogen resistance, and resistance to harsh environmental conditions) have been produced through traditional breeding as well. As a starting point, we need to determine which crops hybridize spontaneously with wild and/or weedy relatives in a given country or region. In cases such as sunflower, squash, and radish, the crop and the weed represent different forms of the same species, and crop-to-wild plant gene flow occurs whenever these forms grow near each other. In sunflower and radish, crop genes are known to persist for many generations in wild populations, even when first- generation wild-crop hybrids produce fewer seeds per plant than wild plants (e.g., Whitton et al. 1997, Snow et al. 2001). Gene flow can also occur when crops and weeds are more Gene Flow Workshop, The Ohio State University, March 5 and 6, 2002 Page 4 Proceedings distantly related, for example between wheat (Triticum aestivum) and jointed goatgrass (Aegilops cylindrica), sorghum (Sorghum bicolor) and johnsongrass (Sorghum halepense), or oilseed rape (Brassica napus) and field mustard (Brassica rapa) (Zemetra et al., 1998; Arriola and Ellstrand, 1996; Jeorgenson and Anderson, 1994). On the other hand, gene flow from maize, cotton, soybean, potato, and many other species is not a problem in the USA because wild or weedy relatives of these crops do not occur nearby. Thus, the extent of gene flow between crops and weeds is expected to vary among crops and geographic regions. Currently, it is not possible to prevent gene flow between sexually compatible species that occur sympatrically. Pollen and seeds disperse too easily and too far to make containment practical. Therefore, it is important to determine which types of transgenic crops have novel traits that might enhance the vigor or invasiveness of wild or weedy relatives or have other detrimental effects. In the short term, the spread of transgenic herbicide resistance may create logistical and/or economic problems for farmers. For example, transgenes that confer resistance to glyphosate (Roundup) or glufosinate (Basta, Liberty) are expected to spread to weedy crop relatives that could otherwise be controlled by these commonly used herbicides, thereby requiring applications of alternative herbicides. Herbicide resistance could also spread to other plantings of the crop and to volunteer or feral crop plants (e.g., Hall et al., 2000). Delaying increases in populations of herbicide-resistant weeds is a basic goal of sustainable agricultural practices. Over the longer term, certain weeds could benefit from transgenes that confer resistance to herbivores, diseases, or harsh growing conditions. Initially, the effects of one or a few transgenes may be difficult to detect unless weed populations are released from strongly limiting factors (e.g., drought stress, salinity). For most weeds, we know little about the extent to which various ecological factors limit the weed’s abundance, competitive ability, or geographic range. This makes it difficult to predict whether transgenic weeds could become more difficult to manage than those that lack novel transgenes. Nonetheless, ecological research can provide helpful information for risk assessment. For each type of transgenic crop, the following questions should be addressed: 1) Will the transgene(s) spread to free-living populations of plants and persist? 2) Are the transgenes likely to enhance the survival or seed production of weedy relatives?Could the proliferation of such transgenic weeds lead to serious environmental or agronomic problems? 3) Could transgene introgression affect the genetic diversity of wild relatives? 4) Are risks outweighed