Molecular Plant Breeding 2024, Vol.15, No.4, 167-177 http://genbreedpublisher.com/index.php/mpb 174 (2) Cultivation of strong restorer lines. Utilize existing high-quality restorer lines from diploid rice, directly doubling their chromosomes, and then crossing them with high-fertility tetraploid rice to obtain strong restorer lines through backcrossing and self-breeding. (3) Utilization of multi-generational heterosis. Studies have shown that the heterosis of hybrid combinations involving neo-tetraploid rice can be maintained at least until the F4 generation. Thus, F1 hybrids can be used for seed propagation, and the F2 to F4 generations can be utilized for production, addressing the issue of only being able to use the F1 generation's advantage in traditional diploid rice and significantly reducing seed production costs (Chen et al., 2022). It should be noted that, to date, the precise molecular mechanisms underlying the high fertility of both PMeS tetraploid rice and neo-tetraploid rice remain unclear. Long-term research is needed to further understand their fertility. Interestingly, recent studies have observed a small number of meiocytes showing 24 bivalent pairing in neo-tetraploid rice, suggesting the possibility of developing new diploid rice germplasm containing 48 chromosomes (Liu et al., 2023). 6.2 Addressing ecological and environmental concerns While the potential benefits of autotetraploid rice hybrids are significant, it is essential to consider the ecological and environmental impacts of their widespread adoption. The introduction of genetically modified organisms (GMOs) into the environment can have unforeseen consequences on biodiversity and ecosystem balance. For instance, the use of TGMS lines developed through gene editing may require careful monitoring to prevent unintended gene flow to wild rice species or other crops (Chen et al., 2022). Additionally, the increased vigor and yield of autotetraploid rice hybrids could lead to changes in agricultural practices, such as increased use of fertilizers and water resources, which may have environmental repercussions. Therefore, it is crucial to conduct comprehensive ecological risk assessments and develop sustainable agricultural practices to mitigate potential negative impacts. 6.3 Policy and regulatory considerations The successful implementation of autotetraploid rice hybrids in agriculture will require supportive policy and regulatory frameworks. Given the use of gene editing technologies, such as CRISPR/Cas9, in developing these hybrids, it is essential to address regulatory challenges related to GMOs. Policymakers need to establish clear guidelines for the approval, cultivation, and commercialization of genetically modified autotetraploid rice hybrids to ensure their safe and responsible use (Chen et al., 2022). Additionally, there should be policies in place to protect the intellectual property rights of researchers and breeders who develop these innovative hybrids. Public awareness and acceptance of genetically modified crops will also play a critical role in the successful adoption of autotetraploid rice hybrids. Therefore, transparent communication and education efforts are necessary to inform stakeholders about the benefits and risks associated with these advanced breeding technologies. Acknowledgments We extend our sincere thanks to two anonymous peer reviewers for their invaluable feedback on the manuscript, whose evaluations and suggestions have contributed to the improvement of our manuscript. Funding This work was supported by the grants from the Central Leading Local Science and Technology Development Project (grant nos. 202207AA110010) and the Key and Major Science and Technology Projects of Yunnan (grant nos. 202202AE09002102). Conflict of Interest Disclosure The authors affirm that this research was conducted without any commercial or financial relationships that could be construed as a potential conflict of interest.
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