Rice Genomics and Genetics 2024, Vol.15, No.3, 106-120 http://cropscipublisher.com/index.php/rgg 116 The salt-tolerant line DJ15, derived from a cross between Dongxiang wild rice and a cultivated variety, showed improved salinity tolerance. QTL mapping identified key QTLs and candidate genes responsible for this trait (Quan et al., 2018). Wild Oryza species, such as O. rufipogon, O. coarctata, O. latifolia, and O. alta, have been identified as valuable sources of salinity tolerance traits. The results showed that these species possess mechanisms for efficient Na+ sequestration and K+ retention, which are crucial for salinity tolerance (Solis et al., 2020). 7.3 Yield and quality enhancement Developing high-yielding varieties has always been a primary focus of breeding programs. During the Green Revolution, the introduction of semi-dwarf varieties like IR8 significantly increased rice yields. The success of IR8 lay in its vigorous growth, high fertilizer response, and yield that was markedly higher than traditional varieties, benefiting rice-producing countries worldwide. In recent years, the integration of genes from wild rice species has further enhanced yield potential. The introgression gene pool of AA genome Oryza species includes high-yield traits such as grain size and thousand-grain weight, providing genetic resources for developing high-yielding rice varieties (Zhang et al., 2022). Wild species like Oryza rufipogonalso offer rich genetic diversity for yield-related traits. Pre-breeding methods and molecular breeding techniques are used to transfer these valuable genes into cultivated varieties. Pre-breeding involves creating intermediate germplasm to introduce beneficial genes from wild rice into cultivated rice, laying the foundation for further improvement. Molecular breeding techniques, such as marker-assisted selection (MAS) and genome editing technologies like CRISPR-Cas9, significantly accelerate the introduction and integration of these genes (Badri et al., 2022; Gautam et al., 2023). MAS utilizes molecular markers to quickly identify and select individuals carrying target genes, enhancing breeding efficiency and accuracy. Genome editing technologies allow breeders to precisely modify or insert specific genes, further boosting the potential for rice variety improvement. Improving the nutritional quality of rice is crucial for addressing malnutrition. Progress has been made in enhancing the nutritional content of rice by utilizing genetic resources from wild and traditional rice varieties. The development of Golden Rice, which is rich in vitamin A (β-carotene), involved the introduction of genes from maize and a common soil bacterium. This biofortified rice aims to tackle vitamin A deficiency in developing countries. Similarly, by incorporating genes from wild and traditional varieties, high-iron and high-zinc rice varieties have been developed, providing a more nutritious staple food for populations deficient in these micronutrients. By leveraging the genetic resources from wild and cultivated Oryza species, significant improvements in disease resistance, abiotic stress tolerance, yield, and nutritional quality of rice can be achieved. These strategies are essential for sustainable rice production and global food security. 8 Future Prospects and Challenges 8.1 Emerging technologies in rice improvement The future of rice improvement is closely tied to the advancement of emerging technologies. Genome editing tools, particularly CRISPR/Cas9, have revolutionized the field by enabling precise modifications in the rice genome to enhance desirable traits such as yield, stress tolerance, and disease resistance (Zafar et al., 2020). Recent developments in genome editing, including CRISPR-directed evolution and base editors, have further expanded the potential for crop improvement by allowing more efficient and accurate genetic modifications (Mishra et al., 2018). High-throughput phenotyping platforms, utilizing drones, sensors, and imaging technologies, allow for rapid and accurate assessment of phenotypic traits in large breeding populations. These platforms facilitate the collection of detailed data on plant growth, development, and response to environmental stresses, accelerating the selection process for desirable traits. Additionally, the concept of de novo domestication of wild allotetraploid rice presents a novel approach to developing new rice varieties with enhanced genome buffering and environmental robustness (Yu et al., 2021). The integration of these advanced technologies with traditional breeding methods holds great promise for the future of rice improvement.
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