Abstract: The crop breeding by genetic engineering (GE) or the widely accepted terms of ‘Precise Breeding’ are the techniques based on the human desire to modify crop traits with precise characteristics of known inserted DNA and protein sequences, anticipated function, and defined insertion sites in the genome of a given species. The acreage of GE crops has reached to 185.1 million hectares world-wide in 2016, which increased almost 100 folds compared with that in 1996, the year of starting commercialization of GE crops. This indicates that the GE is the fastest developing technology in the history of agriculture, which has provided significant economic, social and environmental benefit to the world. In the process of development and commercialization of GE crops during recent three decades, huge amount of scientific data and experiences have also been accumulated regarding their risk assessment and regulation. However, many unscientific burdens still exist that needs to be further reformed. In particular, the rapid development of new products derived from such as genome editing has also raised questions on how to evaluate and regulate them. Theoretically and practically, the GE as a technique, has posed no intrinsic unique or incremental risks comparing with that of the traditional breeding techniques. From scientific point of view, it is common that the GE crops are inadequate- or over-regulated in the recent 30 years. In fact, so far, a risk-based classification and regulation on GE crops has not been fully implemented. Not only the European ‘Process-based’ regulation should be eliminated, but also the US ‘Product-based’ regulation has a space for further improvement. Nowadays, the innovation and reformation in this field based on science has become a common trend internationally. In this paper, some scientific issues associated with environmental and food safety of GE crops are addressed, including what is the proper object for risk assessment (transformed event, variety or species?), the effect of Bt protein on target and non-target organisms, the potential impact of transgene flow, the toxin, allergenicity, compositional change and un-expected effects, and the marker genes and plant pathogen derived DNA sequences in the GE cops. All of these are discussed based on the current scientific knowledge, by which the major focus point in the risk assessment are discussed. Finally, a regulatory framework based on risk classification, which integrally determined by the species that either used as donor or recipient, the genes that confer specific traits and the environment into which the GE crop introduced, is proposed. The possible products belonging to the category of low, mediate or high risk are listed individually. In terms of species, whether the donor or recipient of a transgene has a long history of safe use, does it contain any known toxins, allergens or anti-nutrients should be carefully assayed. Considering the source of transgene, the GE crops can be classified into three categories of intragenesis, cisgenesis and transgenesis. The intragenesis are the gene modifications or transfers within the same species, e.g. the most crops derived from genome editing exhibiting gene silence, knock-out, modification or insertion with no or very low risk. The cisgenesis are the gene transfers between sexual compatible species that may pose low risk. While the transgenesis transfer genes between sexual incompatible species that may present mediate or higher risk. In terms of environmental safety, the risk assessment should be focused on whether there is any sexual compatible wild species or weeds existed in the environment in which the GE crops are going to be released, whether the crossing and backcrossing between crop-to-wild would cause gene introgression that may lead to the selective competitiveness of the hybrids, whether the region in which the GE crops are intend to release is the origin of a given species, etc. All of these issues have to be considered as major focuses in the risk assessment and regulation of GE crops.

Key words: genetically engineered crops, genome editing, risk assessment, environmental safety, food safety, regulatory framework