Abstract
ABSTRACT: Gene stacking refers to the introduction of two or more transgenes of agronomic interest in the same plant. The main methods for genetically engineering plants with gene stacking involve (i) the simultaneous introduction, by the co-transformation process, and (ii) the sequential introduction of genes using the re-transformation processes or the sexual crossing between separate transgenic events. In general, the choice of the best method varies according to the species of interest and the availability of genetic constructions and preexisting transgenic events. We also present here the use of minichromosome technology as a potential future gene stacking technology. The purpose of this review was to discuss aspects related to the methodology for gene stacking and trait stacking (a gene stacking strategy to combine characteristics of agronomical importance) by genetic engineering. In addition, we presented a list of crops and genes approved commercially that have been used in stacking strategies for combined characteristics and a discussion about the regulatory standards. An increased number of approved and released gene stacking events reached the market in the last decade. Initially, the most common combined characteristics were herbicide tolerance and insect resistance in soybean and maize. Recently, commercially available varieties were released combining these traits with drought tolerance in these commodities. New traits combinations are reaching the farmer’s fields, including higher quality, disease resistant and nutritional value improved. In other words, gene stacking is growing as a strategy to contribute to food safety and sustainability.
Highlights
The use of genetically modified crops (GMC) presents numerous advantages to the producer and to the consumer, as realized in greater productivity, reduced use of chemicals, cultivation of plants in adverse environmental conditions and higher nutritional quality (RANI & USHA, 2013)
The first transgenic plants released commercially were engineered for herbicide tolerance and this remains the predominant characteristic of transgenic crops
This technique is described as co-transformation and can be separated into two subgroups according to the methodology used: (1) when all genes are present in the same plasmid it is called “co-transformation with single plasmid” and (2) when genes are in separate plasmids it is called “co-transformation with multiple plasmids” (FRANÇOIS et al, 2002)
Summary
The use of genetically modified crops (GMC) presents numerous advantages to the producer and to the consumer, as realized in greater productivity, reduced use of chemicals, cultivation of plants in adverse environmental conditions and higher nutritional quality (RANI & USHA, 2013). The continued increase in GMC implementation in agriculture resulted in economic and environmental benefits, health improvement and social gains (ISAAA, 2018). Advances in genetic transformation technologies, as well as the explosion of genomic sequencing technologies, have facilitated the introduction of multiple genes and characteristics in a single variety using gene stacking strategies (LUNDRY et al, 2013). There has been an increase in the new development of crops with multiple genes in relation to those with single-gene engineered traits (LUNDRY et al, 2013; ISAAA, 2019)
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