The ongoing discussion on the co-existence between genetically modified (GM) and non-GM crops becomes more important in the European Union (EU). With the recent inscription of 17 GM maize varieties in the common EU catalogue of varieties of agricultural plant species, the acreage of transgenic maize for market purposes is expected to increase in some European countries. In the EU, specific tolerance thresholds have been established for the adventitious and technically unavoidable presence of GM material in non-GM produce, and member states are elaborating legal frames to cope with co-existence. As maize is a cross-pollinated crop relying on wind for the dispersal of its pollen, technical management measures will be imposed to reduce cross-fertilization between transgenic and non-transgenic maize. Various biological, physical and analytical parameters have been identified to play a role in the study of cross-fertilization in maize. This variability may hamper the comparison between research results and may complicate the definition of appropriate isolation distances and/or pollen barriers in order to limit out-crossing. The present review addresses these parameters and proposes containment measures in order to not exceed the legal labeling thresholds in maize.

Cassava is an important subsistence crop grown only in the tropics, and represents a major source of calories for many people in developing countries. Improvements in the areas of resistance to insects and viral diseases, enhanced nutritional qualities, reduced cyanogenic content and modified starch characteristics are urgently needed. Traditional breeding is hampered by the nature of the crop, which has a high degree of heterozygosity, irregular flowering, and poor seed set. Biotechnology has the potential to enhance crop improvement efforts, and genetic engineering techniques for cassava have thus been developed over the past decade. Selectable and scorable markers are critical to efficient transformation technology, and must be evaluated for biosafety, as well as efficiency and cost-effectiveness. In order to facilitate research planning and regulatory submission, the literature on biosafety aspects of the selectable and scorable markers currently used in cassava biotechnology is surveyed. The source, mode of action and current use of each marker gene is described. The potential for toxicity, allergenicity, pleiotropic effects, horizontal gene transfer, and the impact of these on food or feed safety and environmental safety is evaluated. Based on extensive information, the selectable marker genes nptII, hpt, bar/pat, and manA, and the scorable marker gene uidA, all have little risk in terms of biosafety. These appear to represent the safest options for use in cassava biotechnology available at this time.

Despite all the achieved benefits and potential promises from recombinant DNA technology of plants, the potential of transgene spread to wild relatives and to non-transgenic crops is still of a wide-spread concern. We continue to develop recoverable block of function (RBF) technology for gene flow control in transgenic plants. RBF consists of two elements: blocking construct (BC) and recovering construct (RC). Natural expression of the BC (barnase) in embryos and sprouts blocks a physiological function essential for survival or reproduction of the transgenic plant (mRNA synthesis and germination). Artificially induced (heat shock treatment) RC (barstar) recovers the blocked function enabling transgenic plant to reproduce. In natural conditions without artificial induction of RC the transgenic plant can not reproduce itself. However, a single RBF may still fail because of the potential for mutations and gene silencing of the inserted constructs. To minimize the frequency of such an inactivation, we developed a double RBF, in which a single insert comprising two BC, flanking a transgene of interest, was constructed and transferred into tobacco (Nicotiana tabacum (L.)). We used a barstar gene driven by a heat shock or 35S promoter as a RC, and two different promoters were used for barnase genes in the BC. One BC contained a seed germination specific cysteine endopeptidase promoter (BC1) and the other contained the cruciferin promoter (BC2), which is active during fruit development and embryogenesis. Three alternative constructs of double RBF are described, and a segregating two-insert as well as a one-insert cassettes, were compared. One-insert system comprising two BC with different nucleotide sequences but degenerate codons that expressed the same Barnase protein appeared to be the most reliable choice. The biological and molecular data obtained suggest that double RBF is a potent transgene containment technique that can safely be applied in agriculture.

Non-target organisms associated with the soil might be adversely affected by exposure to the Cry1Ab protein from Bacillus thuringiensis (Bt) in transgenic corn (Zea mays L.). To check for such exposure, we used ELISA to test for Cry1Ab in ground beetles collected live from fields with Bt corn residues and Bt corn (Bt/Bt), Bt corn residues and non-Bt crops (Bt/non-Bt), or non-Bt corn residues and non-Bt crops (non-Bt/non-Bt). In fields with Bt corn residues (Bt/Bt and Bt/non-Bt), Cry1Ab was present in all seven species of ground beetles examined (Agonum placidum, Bembidion rupicola, Clivina impressefrons, Cyclotrachelus iowensis, Harpalus pensylvanicus, Poecilus chalcites, and Poecilus lucublandus). For the two most abundant species, P. chalcites and P. lucublandus, the proportion of beetles with Cry1Ab was significantly higher in Bt/Bt fields (0.50–1.0) and Bt/non-Bt fields (0.41–0.50) than in non-Bt/non-Bt fields (0.0). This is the first field evidence that some ground beetle species are exposed to Cry1Ab. The implications of exposure on the performance of these non-target organisms are unclear.