Molecular Plant Breeding 2024, Vol.15, No.4, 198-208 http://genbreedpublisher.com/index.php/mpb 204 6.2 Regional impacts and specific examples The regional impacts of incorporating exotic traits into maize hybrids are evident in various studies. In Uganda, the genetic gains in maize yield and key agronomic traits from 2008 to 2020 were significant, with CIMMYT entries showing a gain of 1.98% per year or 106 kg/ha/year (Asea et al., 2023). This underscores the importance of public-private partnerships in the development and delivery of new genetics to farmers. Similarly, in China, the genetic improvement in maize yield from the 1980s to the 2010s was substantial, with a global gain in yield potential of 559.3 kg/ha/year or 3.4% per year of release (Liu et al., 2021). These examples illustrate the positive regional impacts of integrating exotic germplasm into local breeding programs. 6.3 Lessons learned from failed attempts Despite the successes, there have been challenges and lessons learned from failed attempts to incorporate exotic traits into commercial hybrids. One key lesson is the importance of understanding the genetic mechanisms and environmental interactions that influence hybrid performance. For example, the study by Yu et al. (2020) highlighted that heterosis is a trait-dependent and environment-specific phenotype, and the response of parental lines and their hybrids to environments resulted in various levels of heterosis. This indicates that careful selection and testing of hybrids in target environments are crucial for successful integration of exotic traits. Additionally, the study by Kamara et al. (2020) found no significant correlation between genetic distance and hybrid performance, suggesting that genetic diversity alone is not a reliable predictor of hybrid success. These insights emphasize the need for comprehensive evaluation and targeted breeding strategies to overcome the challenges associated with incorporating exotic germplasm into commercial maize hybrids. 7 Challenges and Limitations 7.1 Genetic incompatibility and linkage drag One of the primary challenges in utilizing exotic varieties for maize genetic improvement is genetic incompatibility and linkage drag. The introduction of exotic germplasm often results in the transfer of undesirable traits along with the desired ones due to the close genetic linkage of these traits. This phenomenon, known as linkage drag, can significantly hinder the breeding process by introducing deleterious alleles that negatively impact yield and other agronomic traits (Hao et al., 2020). For instance, while exotic germplasm can introduce beneficial traits such as drought tolerance, it may also bring along traits that reduce overall plant vigor or increase susceptibility to diseases (Goldstein et al., 2019; Liu and Qin, 2021). 7.2 Complexity of trait expression The expression of complex traits, such as yield and stress tolerance, is governed by multiple genes and their interactions with the environment. This complexity makes it challenging to predict and select for these traits accurately. Advances in genomic tools and molecular breeding techniques, such as CRISPR/Cas9 and genome-wide marker-assisted selection, have provided more precise methods for trait improvement. However, the polygenic nature of these traits still poses significant challenges in achieving consistent and predictable outcomes (Jiang et al., 2019; Lorenzo et al., 2022). The integration of multi-omics approaches and advanced phenotyping is essential to better understand and manipulate these complex traits (Gedil et al., 2019; Liu and Qin, 2021). 7.3 Economic and logistical barriers The economic and logistical barriers associated with the use of exotic germplasm are substantial. The process of identifying, acquiring, and integrating exotic germplasm into breeding programs is resource-intensive and time-consuming. Additionally, the need for extensive field trials across multiple environments to evaluate the performance of new hybrids adds to the cost and complexity (Rogers et al., 2022; Nyoni et al., 2023). Public-private partnerships and international collaborations are crucial to sharing resources and expertise, thereby mitigating some of these economic and logistical challenges (Ying et al., 2019; Prasanna et al., 2021). 7.4 Regulatory and intellectual property issues Regulatory and intellectual property (IP) issues also pose significant challenges in the use of exotic germplasm. The introduction of new genetic material often requires compliance with various national and international regulations, which can be cumbersome and time-consuming. Moreover, the IP rights associated with new varieties
RkJQdWJsaXNoZXIy MjQ4ODYzMg==