Maize Genomics and Genetics 2024, Vol.15, No.2, 49-59 http://cropscipublisher.com/index.php/mgg 54 Figure 2 Comparison of the flow of annual research net benefits generated by conventional and marker-assisted inbred line conversion schemes (Adopted from Morris et al., 2003) Image caption: The marker-assisted scheme (MAS-A) features larger up-front investment costs (larger negative annual net benefits in years 1-6), but because marker-assisted selection accelerates the line conversion process, varieties based on the converted line are released earlier and adoption by farmers occurs sooner. Positive annual net benefits generated by the marker-assisted line conversion scheme are therefore moved forward in time (Adopted from Morris et al., 2003) 4.3 Trait improvement and yield Both conventional breeding and genetic engineering have achieved significant improvements in maize traits and yield. Conventional breeding has successfully increased yields through hybridization and selection, focusing on traits like disease resistance, drought tolerance, and nutrient efficiency. Quality Protein Maize (QPM), which addresses nutritional deficiencies, is a notable success of conventional breeding (Tandzi et al., 2017). Genetic engineering has introduced traits such as Bt toxin for pest resistance and glyphosate resistance for herbicide tolerance, which have significantly enhanced yield stability and reduced reliance on chemical inputs (Wisniewski et al., 2002). 4.4 Environmental impact The environmental impacts of conventional breeding and genetic engineering are complex and context-dependent. Conventional breeding generally maintains broader genetic diversity within crop populations, which can enhance ecosystem resilience. However, it often relies on extensive field trials and the use of chemical inputs to manage pests and diseases. Genetic engineering can reduce environmental impact by decreasing the need for chemical pesticides and herbicides through the introduction of resistant traits (Hong et al., 2019). Nevertheless, there are concerns about potential gene flow from genetically modified crops to wild relatives and non-target species, which could have unforeseen ecological consequences (Weber et al., 2007). 4.5 Socio-economic considerations The socio-economic implications of conventional breeding and genetic engineering in maize are significant. Conventional breeding is often more accessible to resource-poor farmers and public breeding programs due to lower initial costs. It supports local agricultural practices and biodiversity by utilizing locally adapted varieties (Jumbo et al., 2011). Genetic engineering, while potentially more cost-effective in the long term, requires substantial initial investment in technology and expertise, which can be prohibitive for small-scale farmers.
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