1. Introduction

The modern biotechnology era as applied to crop production was initiated by molecular marker-assisted selection to select agriculturally important traits [1]. Other developments

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and eproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

included recombinant DNA technology which helped breeders by providing a diverse gene pool for trait selection, targeted deletion or insertions of genes into genomes, and site-directed mutagenesis to modify gene functions [2]. GM crops have been developed over the years for improvement of desired traits for enhanced agricultural production, as well as to facilitate reduced use of agricultural pesticides [3]. The technology employed to produce GM crops has been described as advantageous when compared to conventional plant breeding, since the desired traits can be obtained in a relatively shorter period of time. In addition, the technology may enable the introduction of desired characteristics that cannot be accomplished solely through conventional plant breeding.

contain allergens and the possible development of antibiotic resistance from the utilization of GM products [7]. Genetically, concerns about GM crops include the possible unintended transfer of genes from GM to non-GM crops or to their wild type relatives, the evolution of GM crops into becoming weeds, the direct and indirect impact of GM crops on non-target species, environmental risks associated with GM crops, and the impact of GM crops on genetic diversity [8]. Directed at the small-scale and resource-poor farmers, the highlighted concerns also include hindrances that may result in limited access to seeds created by patents on the GM crops [9]. Furthermore, contrary to the highlighted benefits of GM crops, crops with enhanced resistance have been viewed as having a one-sided benefit to commercial farmers that grow

Molecular Approaches to Address Intended and Unintended Effects and Substantial Equivalence of Genetically…

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the crops and companies that own the production technologies [8, 10].

genetic changes in the host genome.

3. Transformation techniques used for the production GM crops

Transgenic technology deals with the integration of exogenous DNA into the plant genome using gene transfer technologies [11]. While newer methods such as nanoparticle-mediated delivery are in development, two methods are predominantly used for exogenous DNA transfer into plants; Agrobacterium-mediated transformation and particle bombardment. The first is an indirect or vector-based transformation method, and utilizes the ability of Agrobacterium tumefaciens bacteria to copy and transfer a specific portion of DNA (T-DNA) present on a tumor-inducing (Ti) plasmid into the nucleus of the plant cell. This allows for the integration of the DNA into chromosomes and subsequently leading to the integration of the T-DNA into the plant genome. This type of transformation involves three stages [12]. The initiation stage entails the insertion of the gene of interest into a suitable functional construct. The construct includes the gene expression promoter, gene of interest, selectable marker as well as codon modification. The initiation stage then continues to the insertion of the transgene into the Ti-plasmid. The final step of the initiation stage involves the insertion of the T-DNA, which contains the transgene, into Agrobacterium. The next stage is the bacterium-to-plant transfer during which the transformed bacteria are mixed with plant cells to facilitate the transfer of T-DNA into the plant genome. The final stage is nucleus targeting where the transgene is randomly integrated into the plant chromosome. Following nucleus targeting, non-homologous end-joining processes [13] enables the integration of T-DNA into the plant genome in the absence of any homology between the T-DNA and plant DNA sequences [14]. The possible need for tissue culture steps on selective artificial media associated with Agrobacterium transformation may lead to somoclonal variations, which in itself may lead to

In contrast, biolistic transformation is commonly used to transform plants that are not susceptible to Agrobacterium transformation [15]. The integration of transgenes into a host plant genome, following particle bombardment, generally occurs non-randomly at AT-rich regions carrying nuclear matrix attachment region (MAR) motifs [16]. These elements have been postulated to be target sites for transgene integration into the host plant genome [16, 17]. Their

In view of the global population increases, factors that have been considered important to cope with the increasing food demand include the development of crop varieties with improved nutrition and high yield in different climatic conditions, development of varieties that require the use of less water and fertilizers, and the production of varieties with enhanced resistance against abiotic and biotic stresses [4]. Moreover, new varieties should exhibit high storage quality and appropriate features for processing and market consumption. Specific traits that have been used to improve crops include herbicide - and insect resistance, salt and drought tolerance, increased yield, high protein content and vitamin A enrichment.

Pest-resistant and herbicide tolerant varieties were the first products of GM technologies and they were commercialized in the mid-1990s. In general, farmers have widely accepted GM technologies and the use of GM crops has expanded rapidly in developing countries [5]. The expected expiration of patents on earlier varieties of GM crops will serve as an opportunity for other companies to produce alternative varieties that may compete within the GMO market, thus challenging existing GM varieties. In addition, it will elicit innovative competition in terms of traits to be investigated which were previously not considered. It is therefore important to ensure that existing and future GM crops and - products created through recombinant DNA technology are assessed with regards to any potential risk they may have on human, animal and environmental health.
