Rice Genomics and Genetics 2024, Vol.15, No.3, 106-120 http://cropscipublisher.com/index.php/rgg 109 The spread of rice cultivation followed major waterways and trade routes, such as the Silk Road, facilitating the dissemination of rice to the Middle East, Africa, and Europe. At the same time, maritime routes enabled the distribution of rice varieties to Southeast Asia, the Pacific Islands, and eventually to the Americas through the Columbian Exchange. Rice domestication is believed to have occurred independently in multiple regions, leading to the formation of various subspecies and local varieties (Zhang et al., 2021). The multi-origin model is supported by genetic evidence, showing that local variety groups are closely related to wild rice populations from the same geographical origins (Zhou et al., 2022). 4.2 Domestication events and centers The domestication of rice has been a complex process involving multiple events and centers. The primary center of domestication for Asian rice (Oryza sativa) is believed to be the Yangtze River Valley in China, where evidence of rice cultivation dates back approximately 10 000 years. Two major subspecies, indica and japonica, emerged from this center, adapted to different environmental conditions. Indica varieties thrived in the tropical and subtropical regions, while japonica varieties were better suited for temperate climates (Zhou et al., 2022). African rice (Oryza glaberrima) was domesticated independently in the Niger River basin around 3 500 years ago. This domestication event occurred in response to the distinct ecological conditions of West Africa, leading to the development of varieties with unique adaptations to local environments. The domestication process involved the selection of traits such as reduced seed shattering, increased grain size, and improved yield, which were pivotal for the success of rice as a staple crop (Wambugu et al., 2021). The domestication process has been influenced by interspecific hybridization and introgression, which have played significant roles in enhancing the genetic diversity and adaptability of rice (Zhou et al., 2022). For instance, Domestication of wild allo-tetraploid rice (such as Oryza alta) has been proposed as a strategy for developing new staple crops with improved agronomic traits (Figure 1) (Yu et al., 2021). The research team developed a breeding method using gene editing technology to domesticate wild allo-tetraploid rice, resulting in a series of edited tetraploid rice lines that show significant improvements in domestication and agronomic traits. This domestication approach provides a viable strategy for creating new crops, contributing to global food security. 4.3 Impact on genetic diversity The domestication and migration of rice have had profound impacts on its genetic diversity. The narrow genetic base of modern rice varieties, resulting from the limited number of parental lines used in breeding programs, has led to yield stagnation and vulnerability to biotic and abiotic stresses. However, the wild relatives of rice, such as Oryza rufipogon and Oryza glaberrima, possess a wealth of genetic diversity that can be harnessed for rice improvement (Wambugu et al., 2019). These wild species contain genes for resistance to various stresses and have been used to develop introgression lines with valuable agronomic traits (Zhang et al., 2022). Advances in genomics and molecular breeding technologies have facilitated the identification and transfer of these beneficial genes into cultivated rice, thereby broadening the genetic base and enhancing the resilience of rice varieties (Wambugu et al., 2019). Understanding the historical perspectives on rice migration, the domestication events and centers, and their impact on genetic diversity is crucial for developing strategies to utilize the genetic resources from wild and cultivated Oryza species for rice improvement. By leveraging the genetic diversity present in wild relatives and employing advanced breeding techniques, it is possible to enhance the adaptability and productivity of rice to meet the challenges of a growing global population.
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