Field Crop 2024, Vol.7, No.2, 45-57 http://cropscipublisher.com/index.php/fc 50 5.3 Soil health and water use The cultivation of GM maize can have both positive and negative effects on soil health and water use. On the positive side, the reduced need for chemical pesticides can lead to lower levels of soil and water contamination, contributing to overall soil health. For example, the use of GM maize in broiler production in Argentina has been associated with lower impacts on global warming, ozone depletion, freshwater ecotoxicity, and human toxicity (Bennett et al., 2006). However, the impact of GM crops on soil microbial communities and nutrient cycling is still not fully understood. Some studies have shown that transgenic plants can release novel proteins into the soil ecosystem, potentially influencing microbial biodiversity and ecosystem functioning (Dunfield and Germida, 2004). Additionally, the management practices associated with GM crops, such as the use of specific herbicides, can affect soil biota and crop litter decomposition, although these effects are often transient and influenced by environmental conditions (Powell et al., 2009). In summary, the use of genetically modified maize in sustainable agriculture offers significant environmental benefits, particularly in reducing chemical pesticide use and associated environmental impacts. However, the long-term effects on biodiversity, ecosystem health, soil health, and water use require further study to fully understand and mitigate potential risks. 6 Technological Advances in GM Maize 6.1 Advances in transformation techniques and genome editing The development of genetically modified (GM) maize has seen significant advancements in transformation techniques and genome editing. Traditional transformation methods have evolved, incorporating morphogenic regulators to increase transformation frequency and genotype independence. Emerging technologies such as RNA-guided endonuclease systems, double haploid production, and pollen transformation have further enhanced the efficiency and precision of maize transformation (Yassitepe et al., 2021). The CRISPR/Cas9 platform, in particular, has revolutionized genome editing by enabling precise modifications without incorporating transgenic elements, thus addressing many concerns associated with GM crops and facilitating their acceptance and commercialization (Figure 3) (Aziz et al., 2022; Hernandes-Lopes et al., 2023). Figure 3In trans genome editing in maize (Adopted from Hernandes-Lopes et al., 2023) Image caption: First, a haploid-inducer (HI) line (amenable to transformation) is equipped with the CRISPR/Cas machinery targeting a specific locus (A). Next, HI pollen is used to pollinate plants from a non-transformable genotype (B). After fertilization, the CRISPR/Cas machinery encoded by the male parental genome edits the female genome (C). The male genome is degraded, resulting in a haploid embryo containing only the female genome (D). Chromosome doubling is achieved by applying chemical agents, resulting in a non-transgenic double haploid plant harboring the edited female genome (E) (Adopted from Hernandes-Lopes et al., 2023)
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